Thanks everyone for chiming in with some advice. Hopefully I can just recruit the companions and leaving them at the stronghold to progress and develop their personal stories while actually adventuring with my own party, like for example in Mass Effect, where you don't have to take a character at all to exhaust all their conversation, romance them, and finish their quest-line (besides their one personal mission, where it does make sense that you are forced to bring them along).
If bringing the characters along for more than their own personal side-missions is required, I'll go with a first playthrough with the pre-scripted companions and then a second playthrough with a custom party. If the game is as good as I think it will be, I'll probably even try a third "Ironman" run with just the main character, considering by then I'll probably have a very good idea of the game systems and encounters.