I've played with everyone from very experienced (but not optimizer) players to literally brand-new just got into it after playing BG3 players. And ones in-between.
The one thing that I will admit that I haven't seen is an optimizer playing at mid-to-high levels. I guess I can imagine someone who wants to not only optimize their character, but optimize their turn for "maximum effectiveness" with, say, a high-level fighter or monk with a lot of moving parts, who wants to try to knock down someone and then switch weapons and slow them or some other crazy combinations where they want to find out if the first attack succeeds or not before moving on to the next... THAT I guess I can imagine slowing the game down, especially if they're that rare combination of really concerned about choosing one thing IF this happens, and another if THIS happens - as opposed to planning their turn out and doing it... maybe.
I just haven't seen that sort of player in many many years. I'm not sure that I'd put up with it, regardless of "edition". Take your turn. Don't bore other players. Get it done. It doesn't have to be "perfect".