Minsc has a series of comic books. He is still just Minsc.
“Minsc, the legendary Ranger do-gooder with a heart of gold, brain of lead, and hamster of pronounced wisdom.â€
Don’t expect him to be any different in BG3.
There is no reason why Minsc couldn’t or shouldn’t be gay if the player wants to romance him.
Don't you think it would be dull to beat this petrified horse... again, after BGI&II?
He may be the old good companion he always was, but comic relief dialog would not look good with the current plot. It's not a swashbuckling adventure at all, even compared to BG II storyline and theme.
As for "if the player wants to romance" I'm of an opposite view, it's character inconsistency for me, in this case. When an NPC can have any kind of romance on a PC's whim, it makes the NPC less believable.
