Yamato more probably scales on YC2 level right now.
Ace allegedly took on Yamato about prior to take on Jinbe and it was presented as a stalemate, however it was probably Ace > Yamato by some amount. Overall I seriously doubt Ace grew consistently more than Yamato before meeting Jinbe which occurred soon later it would appear. Yamato however probably grew more consistently than Jinbe did during these years, due her specific environment, and she can use her devil fruit power.
Yamato > Jinbe by a fair extent is very likely to me.