I will agree with criticism Larian’s loose adaptation when it comes to misrepresenting monsters.
XP though is a bit different matter. Computer experience will be different that Tabletop and more combat heavy, as being the most robust system that is what computer RPG can take best advantage off.
The game needs to provide an appropriate progression and that means tweaking numbers (xp gained per kill, or xp necessary per level up). If Larian didn’t do that than they would have to match content they make to 5e xp progression table and that would be silly (we want to add more content, but we can’t because we already have too much XP in this chapter!).
So the thing to do it is make content, see how much xp players can gain on their playthrough, see how you want them to level up and adjust numbers appropriately (xp per kill, quest or/and xp needed to level up).
How xp is distributed is interesting - I think it tells you more of how Larian intends the game to be played, than an inherent design flaw. Solo play is just not supported in the way it was in BG1&2. You can still have freedom to do it, but you don’t seem to get rewarded for doing it in any way.
