I'd say USSJ>SSJ2 in terms of just potential for power. Theoretically, a Saiyan can just continually charge USSJ until his body gives out and that could allow him to pass the SSJ2 multiplayer. But as CC said, it just doesn't become practical in a battle.
Does the manga use the term "destroy" or "blow up?" I would think that any of the attacks capable of blowing up the moon could also do significant, perhaps even permanent damage to the earth as well. If this is the case, Vegeta need only be marginally stronger that Piccolo or Roshi to confirm...
I've only seen the anime prior to reading Moro, but I say Jiren takes this pretty easily. Nothing Vegeta did in that time makes me think he closed that much of a gap yet.
Semi Cell vs Androids 13, 14 and 15. No merging or absorbing.