Ive never played Dnd with "respawning" enemies. In a video game if lets say the voidwoken near fort joy keep on respawning every 5 minutes you could keep on killing them to get infinite exp.
Typically resources (e.g. exp, gold, weapons, enemies, allies, crafting supplies etc ) is 'reasonably' well regulated to avoid certain issues (and yes I know you can finish the game with millions of gold).
I know some players like "farming" for items and exp. I dont think 'farming' that will be a big part of BG3...