I'm thinking that the only Merged character where his SSJ multipliers were not nerfed was Vegetto (Boo). That explains why Vegetto SSJ was impressed with how easily he was defeating Buuhan and humiliated him even being a sweet tooth. It also explains the DBGT string: Vegetto SSJ3 (Boo)> = Goku SSJ4 (Initial) >>>>> SBV1> Vegetto SSJ (Boo)> = Baby Vegeta Base> Goku SSJ3 (Baby) >>> Goku Base (Baby) >> General Rildo Base> Buuhan.
As for Gokhan (Potara) (Boo), it is most likely that his Base state is at least as powerful as Vegetto SSJ (Boo), considering the difference between Ultimate Gohan and Base Vegeta. Surely Gokhan's SSJ multiplier is nerfed, so I have Gokhan SSJ3 (Boo), between Goku SSJ4 (FP) and Vegetto SSJ3 (Boo).
As for Gokhan (BoS), he would be more powerful than Gokhan (Boo), because Goku increased his power too much in all his forms, but anyway Gokhan SSJ3 (BoS) must be inferior to Vegetto SSJ3 (BoS), due to Goku mentioned that not even Fused into Vegetto could against Beerus (Initial).
If we talk about Vegetto (BoS), only his SSJ multiplier on his Base would not be nerfed, but if we talk about his gaps between SSJ2 on SSJ and SSJ3 on SSJ2, he would be nerfed. In this way I have Vegetto SSJ3 (BoS) a little stronger than Gokhan SSJ3 (BoS). Why do I have it that way? Well, Goku only knew the power they had as Vegetto SSJ (not knowing the exact power they had as SSJ2 and SSJ3). The only point of reference that Goku had on the SSJ multipliers in Fusions, was Gotenks. Goku knew the power of Gotenks Base and SSJ (Pre), he also knew the power of Gotenks Base and SSJ3 (Post). Therefore Goku could give an idea about the difference between SSJ3 over SSJ in Fusions. Vegetto when he transformed into SSJ, was amazed at how powerful he became. Since nothing contradicts that a Hypothetical Vegetto SSJ3 (BoS) is stronger than I expected, I prefer to have only its SSJ2 and SSJ3 states nerfed in BoS.
Beerus (Initial) is more powerful than Vegetto SSJ3 (BoS) due to what Goku mentioned. Then we see Vegeta SSJ2 (Enraged) beating Beerus (Initial). 1 year later we see Goku congratulating Base Vegeta for becoming so strong for training with Whis. That Base Vegeta was more or less at the same level as Goku Base (Post God).
What do you think?