You could have a party in NWN. The OC however only allowed you have one henchmen and a summon (as well as their summon if they could summon one). Hordes of the Underdark allowed you to have two party members.
Ah, never made it that far, NWN bored me to tears (and calling it quits) halfway through the campaign, so I obviously never looked at the DLC. I obviously can't comment on how well the parties worked in that DLC either.
