Commenting on max levels if optional rules were used there are ways to kind of extend to level 25 which is more kind of level 30 as there is an optional rules book out there for 5e that does have level 21-25 as well as how to impliment epic boons for an additional sudo 5 levels so its kind of like level 30. But there is nothing that goes beyond that currently effective for 5E. Vs Pathfinder which there is an epic rules book that has no level limit. Similar to never winter which i believe has the ability to go up to level 40. No one really has ever tried to go beyond that on a pc game as really after around level 25-30 creating challenging fights just gets to be extremely pressing as your pretty much talking instant death effects in a lot of cases. Even over 15-16 its very challenging to create good high level encounters for players. A lot of Dungeon masters have difficulties after level 10. Which is why the majority of campaigns end around 10-12 for groups of people.

I have seen it where DM's have been like this is going to kill you if your not careful against parties of level 10 characters and utterly flopping against 1-2 over tuned characters. You can pretty easily pump out 100 damage in a turn with a level 10 character optimized. Which makes encounters very hard to balance without making the encounters very very difficult.

Looking at BG 3 I honestly think the minotaurs currently feel more like a level 5-6 encounter for most people where the spider felt that way more so in the initial play through. When I did that encounter during patch 4 vs the spider I cleared it without taking damage. Where the Minotaur encounter which i underestimated after my first playthrough I actually had to use a rez scroll on one character. With an optimized party.