Freeza, easily. Specially if we're taking the anime into account where everyone is BoGs SSJG level or above. One of Freeza's suppressed forms vs Vegetto would've been a closer match.
Absolutely not. Cell splattered 17 and Piccolo together with no effort whatsoever, 18 isn't changing anything. Hell he even walked through Piccolo's best blast without a single scratch.
I think the team has this. Yamcha is cocky enough that he's getting by Gohan going by the Saibaman fiasco. He won't be as weakened as Raditz since he's stronger, but he'll definitely be at disvantage against Goku and Piccolo.
I have always went by the logic that DBS > Super, so Gogeta would be lucky to beat SSJG Goku. SDBH might have something to say about this, but I haven't watched it.
The novel says no one in existence could defeat SSJ1 Broly, so I think even SSJ1 Gogeta could take this with some difficulty.
Even before Vegeta's training with Beerus, Whis said he didn't know anyone stronger than Goku and Vegeta. UE Vegeta one shots.
SSJ4 Goku, easily. SBV1 is the strongest Ki Goku ever felt, so at least he is above Super Vegetto. I think all the boosts from SBV1 to SBV2 to Golden Oozaru BV to SSJ4 Goku make SSJ3 Vegetto an ant next to SSJ4 Goku.