Toppo probably wins this with minimal difficulty. SSB Vegetto is pretty overrated in my opinion; I honestly feel that even SSJ2 Kefla possesses the capability to wreck him.
As the ToP progressed, both Goku and Vegeta had seemingly far surpassed the caliber they were at when they faced Merged Zamasu. Though the degree of which this took place was shrouded by ambiguity, it seems plausible enough that both Saiyans in their respective forms (SSB Goku Kaioken x20 and Super Saiyan Royal Blue Vegeta) had reached a level that was more or less on par with the SSB Vegetto that took on Zamasu.
Toppo was trouncing Super Saiyan Royal Blue Vegeta, so that in-turn puts him a good deal above SSB Goku Kaioken x20. While neither of these factors undoubtedly secure Toppo a win, they are solid implications that strongly support his prominence on the power scale; given how much Goku and Vegeta had likely progressed. Of course, there is always that chance that neither Saiyan (barring UI Goku) had actually reached SSB Vegetto-tier; in which case, Toppo stomping Vegeta as easily as he did wouldn't merit as much credibility. But all in all, I'd say the odds are definitely in Toppo's favor.