Unfortunately, he does not have a complete brain. As we discussed before, Cell Max not being able to use his power properly, he can't use his 100%, but to lighten things up, Cell Max (Weakened), managed to pull off an amplified attack, which should be at least as powerful as Cell Max's. a hypothetical Cell Max (Complete), but much more powerful even.
I think most of us agree that the Gammas should be superior to Vegeta SSJB (Post Yadart) and UI Sign Goku (Post Merus), considering that Piccolo estimated that the Gammas were just as powerful as Goku and Vegeta, but then Piccolo affirmed that the Gammas are stronger than I expected.
Will Orange Piccolo be as powerful as UI Goku (Arc Moro)?
Will Incomplete Cell Max be as powerful as Mega Instinct Vegeta (Initially against Granolah)?
The difference between Orange Piccolo and Incomplete Cell Max over the Gammas is colossal.
I think both True UI Goku, Mega Instinct Vegeta and Orange Piccolo are at the same level currently. Considering it's been 3 years since the Arc Granolah, I'd like to have all 3 of them in the UI level Goku Avatar Giant (vs. Gas) and Granolah's shot. I have them just below Zombie Gas.
I think both Incomplete and Full Cell Max are somewhere between Buff Zombie Gas and Black Frieza. Perhaps Gohan Beast is the most powerful character in the Universe according to the prophecy of the Oracle Fish.
I think that both in the Movie and in the Manga, Piccolo was aware of the powers of Goku and Vegeta until the Arc Broly (Movie), Arc Moro (Manga), while Gohan was aware of the power of both of them in the present.