On what level(s) would episode 1 Goku be, if he had his later/current power ups, and transformation?

[Psajdak]

For whatever reason Goku, as we see him in the beginning of series somehow is able to use everything from his latest arsenal, but his base power is the same as it was.

How much would those transformations, and tehniques helped him?

[Lionel]

Nothing from Dragon Ball or early Z could touch him. If he's still conditioned to handle the rigours of the abilities he wields currently then every preventable death would be halted in its tracks. The ramifications this has could entail things like Yamcha not becoming as close to him as he did become due to the Dragon Balls still competed for. As well, it's quite possible Piccolo Jr never comes into being as Daimou is doomed from the onset. The Dragon Balls are rendered inert afterwards with no hope of reconstituting them.

Freeza himself would likely need to intervene directly if the adversaries have any hope of putting a dent into this nigh undefeatable monster. Who knows how much Goku has improved since first meeting with Roshi, though. It's possible he could already be powerful enough to crush everything from the Cell arc and more by the time Freeza shows.

[theherodjl]

If Kid Goku had MUI, he'd be stronger and more skilled than the vast majority of pre-DBS characters. Only certain forms of Majin Boo could defeat MUI Kid Goku which means Goku would be unstoppable until Boo's evil half took back control over his own body. The conflict up until that point would depend purely on however much Goku wants there to be conflict.