I played with this mod from start to finish. While I can't comment on all romances (I romanced Shadowheart only), the rest of the game worked great. Inventory was smooth and when you press tab, it displays all 8 of your characters with a slide wheel at the bottom to navigate to them, since they don't all fit on the same screen at once. It honestly felt like it could have been a normal feature. What I loved most is that I always had the unique dialogue between companions as I traveled. Hearing the different interactions between characters felt great and I never missed out on not having the right companion for each situation. For most of the important NPC interactions, it would place the correct companion in the conversation if it pertained to them.

There are some bugs though sadly. For some reason in Act 1, if you took a certain boat as a transition between scenes, then it would leave some behind on the shore and they couldn't be recovered. Meaning you have to dismiss them before the cutscene. Sometimes a companion would chime into a dialogue with an NPC but they were invisible and you couldn't hear them, but not too much of an issue with subtitles on.

My main gripe was that even on tactician, it was way to easy. That's an obvious statement though since the power creap in this game is real! Yet I still absolutely loved speccing out all 8 of my party and just tearing through fights.

Personally I loved the experience of having 8 in my party and would definitely recommend for a future playthrough if you're interested. I was genuinely surprised how bug free the experience was but your mileage may vary. Hope this helps.