I can give a few details without saying anything truly spoiler-ish. In Build 0.6 Oscar will join the hotel's staff, and this happens to everyone regardless of whatever choices you made. You could say he's part of the main story.
As for P and "Nick" (as you called him)... Well, for most players only one of them will remain in the hotel. If at the end of the build you saw a scene of one of them going out of the hotel to have some alone time, that character will leave and get back to their regular life.
If you did not get that scene in your playthrough, you should be able to pick which one you want to join your team. But if you have the Leader background you should be able to get both of them in a single playthrough.