Villain is reg, plays decent for these stakes, donk MW 22%, don't see any other stat that is really relevant here that I might have a sample big enough for.

The 2 questions for me are:

What sizing does our range wanna use on this river if we are gonna get checked to, and what raise size do we wanna use against the line our villain took here?

Regarding the first question I think we should go pretty big as his callingrange should consist of pretty much only flushes and so we are not gonna valuebet any hand that is say worse than Q-high flush here, possibly even K high depeding on villains tendencies and whether he sometimes (or at any frequency) donks river with nutflush in this spot.

Second question however I think we wanna go pretty small, our range in general doesn't contain many hands that we can turn into a bluffraise now especially against a donk, so I think using a minraise sizing with our nut- and straightflush and the rare case where we have the bare Ac+with some backup equity to call the flop is, propably like A54 type of hands that believe not be ahead enough of the time here. In case someone would wanna analyse my range (with say PokerJuice) for this spot to see how many bare Ac hands I am gonna show up here , just assign a 15% for UTG for me here.