For me minmaxer in regards to BG3 are those people who say that you can only play optimal race/class combinations and that everything without maxed primary stat suck, are unplayable, not competent or less hyperbolic, have to constantly struggle, because they miss out on 5% success chance.
Although I would also count people who for example use respec to go in and out of multiclassing depending on what is more optimal like fextralife suggested or use respec to dump a stat once they found a "set stat to 19" item.
That sums it up pretty well I think.
Of course anyone is free to do as they please in single-player, but in multiplayer it could become an issue just as it would be disruptive at the table unless everyone agreed to min/max.
