The biggest difference between DLC and an expansion pack is DLC adds to the already made world/map ie horse armour, skins, guns, companions and what not. Whereas expansion packs are 'usually' a whole new area and/or new short story with a different hero with hours of content.
The first option is the best one. I never liked the idea of Early Access releases. I only have so many hours on this earth (as I am on reddit on another tab while I'm writing this haha) and I prefer to play a game that is finished instead of beta testing it without being paid.
And push backs just friggen suck. The best way is 'when its ready.'