dogeddie: What size party would be realistic, and who do I absolutely need to bring along? Thanks
It's different than BG in the way companions are handled. You can pretty much leave them to do their thing (though you can also issue commands). Also, all companions level up with you, whether in party or not, so they all get their share of XP anyway and you don't win or lose taking them along. Just like KotOR.
In the beginning of NWN2 OC, you get 1 companion and that goes up to.. don't remember, maybe a party of 5 or 6 in the end. Mask of the Betrayer is you and 2 followers.
There are some missions where you have to take one of the companions along and that's always stated in no uncertain terms. Not always the same one, some you have to do with the ranger dude, some need the paladin or priest.