Old One
Arcane
You don't have to worry about that, all the quests (aside from the faction rank progression ones) will be available for you to complete have you joined a faction or not. Playing without joining one for a long time just makes the game unnecessaraly more difficult for you.I would get locked out of faction cities as soon as I commit to a faction, right? In light of this, it does make sense to quest as much as possible with all the factions before committing, right?
My one complaint about the game is that the factions are too well-balanced in terms of likeability, which makes it extremely difficult to pick one. They all have cool things about them, but they're all also slightly distasteful.