I think the big difference between the BG3 companions to say, BG2 companions, is strictly character agency.
For example, Imoen and Aerie both have enough backstories and potential character arcs to play the role of a protagonist - it's just that the original games gives them less agency to drive those things forward, for better or for worst. Their personal goals are basically "help CHARname" and narratively only breaks from the player at extreme reputations or special cases. For example Aerie if your reputation drops too low, or potentially if you have Korgan/Haer'dalis. Though Imoen AFAIK is always loyal.
It definitely smooths out the narrative and makes them more agreeable as they are subservient and basically "working for you" as long as you play within the safe-zone. It places the focus of the story and agency strictly on the player, but at the cost of probably making them a bit less compelling as characters.
Whereas the characters in BG3 will push and grind against your intentions with their own from the very start. They never really feel subservient and are clearly more focused on their own goals, which makes them livelier, but can be frustrating if you're trying to run a smooth ship because they all pull you in different directions. Conflict/friction basically can't really be avoided.
