6 players is too much - it's a multiplayer video game not just a Baldurs Gate sequel. The less players the multiplayer has to handle, the better the experience will be. It means that DMing like you can in DOS2 has more potential of happening.
People do not have the choice of playing with less characters - they will see the space for more characters and assume they are missing out if they don't fill up.
D&D5e is based around a 4 player party. Adding or removing characters affects the difficulty a lot, which I know from DMing the game on an open table for a few years.
Maybe 5 if stretched. Not 6 though. I don't care about half of the characters in any of the classic RPGs with loads of characters. I played Disco Elysium last year and only had a 2 characters max and felt I knew them more than any characters from any CRPG I've ever played. And I've played a lot of CRPGs.
