Who's Who vs Jinbei was a weird fight, because it made both characters look weaker than they really were.
Who's Who being a Lucci-could-have-been, when Luffy already been Lucci, made Who's Who look weak, along with the fact he didn't do much damage to Jinbei, even while having numbers on his side most of the fight.
Jinbei looks weak because Who's Who has no feats: he lost to Shanks's crew, then got bodied by Jinbei. No way to scale him, doesn't do anything for Jinbei.
Oda should have given Who's Who a win against a strong character to prove he's actually strong.
I think Who's Who is much weaker than Queen, but close to Jack's level. Who's Who has good speed: he could dodge Jack's attacks pretty easily, but dodging Queen's lasers would be a lot more of a problem.