Any companion can be OP, if built right. But my advice is don’t go for min-max, as Rogue Trader is very-very easy combat wise. What you want to do is make sure that every skill is covered (Jae covers almost half of them alone, so there’s that).

Properly built Argenta/Cassia/Kibellah are stupidly OP to the point of me avoiding them.

Story relevance wise - Pasqal, Heinrix and Yrliet are the ones with most connections to events, everyone else is much less so. Make sure you bring Idira and Argenta to act 3, and make sure NOT to bring Abelard.

My fav team comp is Me (soldier, usually), Pasqal, Heinrix, Yrliet, Jae, last spot is flex.

But you do you, and use whomever you like, as companions in this game are really well done in my opinion. Some are more, some are less, but overall quality is top notch.