I am planning on doing it as a duo for BG1, If I get to BG2 I might pick up a companion for specific quests for role playing purposes e.g. maybe Nalia for Da'rnise keep, Valgar for Planar Sphere (this would also help slow down XP progression without having to mod XP rewards lower). So If I get to SoA that would mean rushing to Spellhold early to save her which I think would fit with the sisters-dynamic im going with. Might set the gold requirement for spellhold higher to justify getting a tad more XP before going since SCS underdark as a low level duo is pretty ouch.
I played the bhaalspawns team (PC+Imoen + Sarevok in ToB) many times and I really enjoyed it. Happy gaming to you.
Just want to say that I used to be cautious about the xp level before triggering ch.4 because you can get at least two versions of Imoen. The 400K and the 1.2M iirc. Perhaps things have changed in the latest engine version of EE, more exactly post dragonspear release but I doubt it. BG2 and its related tooling are not installed on my computer at the moment. I can't tell you the details but, as an experienced and active player, you may know it by heart.
Such a difference means nothing in the mid/long term, especially in your setting. However, in the very short term, I think that playing with a too noticeable discrepancy between characters is less enjoyable (but perhaps it's just me).
On second thought, with two spellcasters, you probably planned to boost Imoen with a rich collection of scrolls, anyway.
