Please note that all my opinions probably aren't as much objective as I'd want them to be
For starters I'll try to explain how i understand Ki in the series:
For me Ki is the raw energy produced in constant stream by every living cell in ones organism. So to speak each person in the series has different KPS (Ki per second) production. Not to forget about different Ki storing capacity. An untrained warrior has two states of Ki flow: while relaxed and while fighting. A fighting person automatically keeps some buffering Ki around his/her's body like some sort of layer or shield protecting from attacks. Spending Ki to that layer is based purely on instinct and can be raised the same way during blocking or even preparing for a punch. Furthermore each warriors Ki is imprinted with some of his personal traits for example: good or evil. When comparing Ki sensing to other senses we can tell each warrior has his own and in some way unique "scent". But here we must remember that Ki sensing is way more precise and can often be used to read the opponents movements even during fights. For example – we have Kuririn dodging Nappa's attacks in the Saiyan saga. The Earthling felt changes in Nappas Ki and adapted to it.
Here's some questions i want to ask you that developed over the years i spent tracking DB debates across different forums and sites (with my interpretation):
1.Why does the warriors measured level of power increase during performing an energy attack?
I think that the scouter reading during an energy attack can be called full power of a warrior. Standard power level is directly linked to the flow rate of Ki with a constant stream to the outside - KPS (or to be more precise – production per fraction of a second). Ki control or mastery allows to change range, power, structure or in some examples even direction of a Ki attack. I think when the warrior concentrates on the attack each cells KPS increases and Ki can flow with a wider stream. It would be logical to assume (due to the connection Ki has with ones mind and spirit ) that he loses additional Ki to maintain the shape, density and in some cases forcing a deadly cargo in the most compact form. What's more – that rule can also be linked to powering up – a warrior is concentrating to increase his KPS to his personal maximum. Which can't be maintained long cause of the stress it causes to the cells. Each energy has the tendency to disperse so a warrior allowing his Ki to leak from the body must be maximally concentrated (hence ability to project Ki is said to be used by the masters only). Linking all the points a warrior can only perform one full power attack or many weaker and less controlled.
2. What's an aura? Is it a technique or just a visualisation of energy increases?
Aura as an technique is simply absurd to me. It's never stated to give even the smallest profits. During an all out fight when a warrior must force himself to use every fraction of energy, the excess Ki which he couldn't control leaks from his body. So for me the aura is just a projection of this constantly lost energy. I heard some opinions that kaioken is an aura technique and it's the aura that allows the warrior to exceed his potential at that moment. I think kaioken works more like some restriction remover. If we assume that one theoretical cell able to produce immense power is stripped from biologically programmed restrictions and forced to instantly produce several times bigger energy in the same time as before we can also assume that this strain causes necrosis. Thats why Goku instantly increasing his KPS production can't control this huge leak of Ki. Therefore the roaring, chaoticly flaming Kaioken aura. By learning Kaioken he mastered convincing his own body to surpass it's limits (mind over matter guys
).3. Does the energy increase depend from a warrior or from a technique he uses?
I think it's dependant only from the warrior. A technique can influence the shape or charging time but maximum power will always be the same. For example – if Vegeta used final flash or kamehameha against Perfect Cell the energy he'd use would be the same but the effect may vary based on charging time.
4. How much can one increase his power level while concentrating or firing an energy attack?
If we assume that Piccolo and Goku during their fight with Radditz had perfect Ki control we can tell (with some error possibility of course) that the increase is more or less 3- fold. But the 3-fold increase for makkankosappo was a result of a very long cummulation so in a case of firing quicker (like Goku's kamehameha in this fight) we can talk about approximately 2- fold increase. I also think that Piccolo's and Goku's maximum power level (separately) was bigger than the standard power level Radditz showed. But Radditz couldn't control his Ki so his standard level was at the moment his maximum. Good thing that at this time powering up to maximum was a big deal for the good guys cause this way Radditz actually stood a chance. My viewpoint is proven by Vegetas words that Radditz was defeated a bunch of weaklings with a power barely excessing one thousand.
5. How does it look like from an biological viewpoint?
Each cell produces energy which falls with a constant stream to whatever system it uses – nervous, limfatic etc, and through it is spread across entire body. Some warriors are able to control the production and flow of this power to the level over which given cell almost destroys itself (kaioken overcomes that barrier).
6. How much does responding with an energy attack weaken incoming energy wave?
Whatever physical (or mathematical) explanation would be good for me here. Let's say attack A – 1000, attack B- 2000. They clash. Attack A becomes overpowered, a fuckton of energy dissipates and attack B hits the opponent with 1000 force. Of course attacks shaped to explode don't have that stopping power.
7. What kind of damage is dealt by energy attacks?
First, let's introduce some order into different attacks:
a.waves
b.discs
c.beams
d.bombs
Ad. a
From what i've seen waves can be split into three categories: pure energy, flaming and (some kind of) electric. It's hard to tell which type is the most effective. Pure energy can be negated throug energy barriers or protective layers around a warriors body. Each block increasing Ki consumption (or KPS) with for example adrenaline rush will strenghten that barrier. It is best to respond with a similar wave to even slightly weaken the incoming attack. Energy attacks overload opponent cells with energy disintegrating them. The instinctive barrier protecting the cells is purely energy based hence flaming attacks go through it more easily. Accumulated heat can be more damaging when defending warrior is blocking. Of course electric attacks are also pure energy but additionaly they involve spasms of opponents muscles leaving him open to the next attack. I think each type of attack consists from the same kinds of energy( pure, thermal or electrical) but the proportions beetwen them are vastly different.
Ad. b
Discs are centered on maximum conversion of Ki. Thanks to that we obtain very high Ki concentrated on a millimeter (or less – depending of ones mastery of Ki control) thickness. They inflict pure slashing wounds. The huge advantage this kind of attack has is a possibility to kill or heavily wound even much stronger opponent (Kienzan against Freeza or Nappa). Ki concentration (sometimes with an additional rotation) overpowers opponents body local KPS production on given surface. The attack frets the cells whose energy it overpowered. In this moment all depends from what depletes faster: energy of the body absorbing the impact of the attack or the attack itself. Example: Kuririn had just a miniscule fraction af Perfect Cells power so even his most powerful Kienzan he could muster at that moment ( without charging it for a prolonged time) was overpowered by Cells unconcious energy output. Cell's regeneration could have played some part in this but i see the gap beetween them so huge that in my eyes that doesn't make a difference.
Ad. c
Beams work basically the same way as discs. Depending of their cross-section they overpower local energy output. They have one serious flaw though – they must be precisely aimed to hit some vital organ or the agressor must increase the cross-section to maximize hit probability. Type of damage can be compared to high velocity bullet wounds.
Ad. d
Bombs tend to explode. Thats all there is to it. To this category we assign Ki blasts but also attacks such as big bang. What's interesting even the structure of some waves can be altered to explode on impact. Warrior hit with this kind of "package" gets damaged from energy, heat and kinetic impact (classic combo
). The downside is bombs can be easily detonated or deflected with a relatively small blast.8. Does regeneration count as an Ki ability? (Namekians, Cell, Buu)
I think this is plausible. Example: sacrificing an amount of Ki equaling the normal energy of lost cells can regenerate said cells. As for Buu his regeneration was haxed and maybe basing on some kind of magic. Even Piccolo could create something out of nowhere so creatures with more magic in DB universe could have this ability a lot stronger.
9. How come Buu's energy never runs out?
I have no idea. The only one theory that comes to my mind besides magic is that due to this jelly goo he was built of (i seriously doubt Buu was a carbon based life form) Buu somehow replenished energy lost to regeneration with the energy of a new born cell. But since energy just doesnt come from nowhere – maybe he could absorb all kinds of energy surrounding him and add them to its own? That would explain why even after the strongest punches he regenerated quickly – cause kinetic energy from said punches took only a short while being processed and added to his Ki. Energy attacks caused his cells to desintegrate meaning it took him longer to rebuild himself. Genki Dama just overloaded his cells so quickly his organism couldnt keep up with the energy processing. Eventually energy within each of his cells was bigger than the strenght of molecular fixation between separate cells. So each attack ripped cells from Buu and they were floating in a more or less visible lumps and the universal code of these cells allowed them to unite into one organism again. These theories also explain why Good Buu was losing power against Kid. Since Kid was pressing without hesitation all cells Good Buu was losing at a constant rate were dragged towards the stronger energy source which was Kid Buu. Ultimately the difference in powers was so strong that all of the energy at the battlefield was stolen from Good Buu as we see he couldn't regenerate.
10. How did the healing techniques work?
Kibitos powers probably were close to magic as I see him as some kind of divine creature much like Kami, Kaio or Kaioshin. But the powers inherited by Dende practically didn't differ from Kibitos ability. The little guy never showed any loss of energy after healing, even when he healed Mystic Gohan. So we can forget about trading equal amounts of energy since Dende's ki would probably equal 0,0...........1 Gohans at that point. Maybe the healers somehow channeled solar or magnetic energy in a similar fashion Genki Dama does?
11. Is fusion or absorbtion a Ki technique?
Plausible. On some level fusion is a Ki technique cause the only thing the fusion subjects retain is the same energy compacted into smaller form. Maybe this is the source of power for fusions that combined and strenghtened singular cell with added or even multiplied KPS can easily channel much more energy. The absorbtion is different in my eyes though. Furthermore it's different for Cell and Buu. Buu adds absorbed subjects power to his own. Eventually he gets some of this subjects traits – like good nature (Dai Kaioshin), or ability to think logically (Piccolo). As Buu's cells are far from being normal I can't see them merging with normal cells the same way fusion does. Cell on the other hand absorbed humans in the form of liquid. That increased his power (in a linear fashion i think) but even if he absorbed all of them he wouldnt become perfect. For this he needed two organisms specifically designed for this purpose – Jinzoningen #17 and #18. I think they completed his genetic code and allowed him to become "perfect".
12. Is kaioken similar to SSJ?
Probably not. For starters kaioken heavily strained the body. Ssj doesnt have that flaw. I see it like that: each warrior has a limit of ki his body could produce at any given moment. Kaioken breaks this limit forcibly at the cost of destroying ones own body. On the other hand SSJ transforms the body to overcome this limit and set a new one. In my eyes this applies for every transformation we see in the series. So kaioken=technique, SSJ=transformation.
13. Does kaioken has any kind of limit?
Yes and no at the same time. Theoretically even Goku during his fight on earth could use kaioken x200. This would probably last a fraction of a second and Goku would be vaporized in the process. Thats if we assume the Kaioken is an instant increase (which I personally believe). If it requires to come through earlier stages of kaioken then Goku would probably drop dead at x7. It also depends what kind of organism we talk about. First come the Earthlings and Saiya-jin cause their genetic structure is similar to the degree allowing both species to reproduce with eachother. Earthlings – weaker than Saiyans didn't have large power levels and all the shown examples couldn't probably use kaioken stronger than x30 without dying (and this is giving them too much credit I think). The Saiyans on the other hand had SSJ transformations giving them more power than the strongest kaioken they could muster in base state (and without the extremely rapid energy consumption and destroying their own body). Eventually we can assume they could overcome their own strength as Ssj (or SSJ 2-3 ) but it would drain their Ki instatly before the fight would even start. Then we have other controversial races like Namekians, Changelings or even individuals like Cell and Buu. We can only guess how their organisms work not to mention some of them have abilities dangerously close to being called magic. Even then I don't think they could use kaioken much more efficiently than Goku. Buu is the extreme example out here because of his ridiculous regeneration ability. He probably could compensate with his cells for absurdly high levels of kaioken and the second he stops using it he starts to regenerate. So as long as he's smart enough not to vaporize himself i could see kaioken Buu being the strongest in the universe.
14. How does ki sensing work?
Earlier I compared sensing ki to the sense of smell. But more accurate would be to say that sensing Ki is like seing a bright light. It's impossible to say numerically how strong something shines. The only character capable of this was #16. Just because he had an electronic device installed. Thats why all the characters without scouters only say about a probable range of power for the person they sense – weaker than me, more or less equal, stronger than me. Whats more there are examples that once you're heavily outclassed, the only way to describe the opponents ki is HUGE! or MONSTROUS!. When comparing two beings that "shine" much brighter than yourself your estimates aren't probably even remotely close to their real powers cause they both blind you at that moment. Lets look at Goku and Mirai Trunks first encounter. They were hardly even (Goku blocked all of opponents slashes without moving anything but his right hand) yet the reactions everyone displayed witnessing this clash were totally one sided – that both SSJ have enormous but equal power. You don't see the difference beetween the stars, do You? Yet each of them shines with a different magnitude. Other examples – two lightbulbs – unless one of them is 40W and other 100W you can't really tell the difference just by looking at them. Now imagine you're seing two even stronger lights. Both blind you at the first sight – can you tell which one is stronger just by looking at them? No. One must take into consideration other factors. Feeling Reiatsu in Bleach would also be a good example but I'm aware that not everyone have seen it. It would explain some of the reactions when someone felt a big Ki. The ones that cross my mind right now:
-Goku saying he feels a bunch of huge Ki's when he arrived on Namek
-Piccolo, Gohan and Kuririn unable to tell the difference beetween Vegeta pre and post zenkai on Namek until he actually starts fighting
-Goku describing Vegetas Ki as huge after he performed kaioken on Earth
-all good fighters unable to tell that Perfect Cell powering in front of their eyes is weaker than Gohan SSJ2
-all of them couldn't tell the difference beetween SSJ Goku and SSJ Vegeta in the android saga
-Piccolo suposedly being in the same range as the SSJ according to Kuririn
-Piccolo (and everyone else) amazed by Gotenks SSJ yet Piccolo is still sceptic and wants to see Gotenks in action.
-Gotenks base after RoSaT supposedly being uber strong
There are probably more examples but you understand what I mean at this point. What are Your opinions?
Congrats for getting to this point
Yes - my goal was to bore You all to death so i would be the one and only Daizex user... 
