Are we playing as a totally new main character or is it the same person from the first one? Just wondering

I'd think it's the same character since there were at least 3 portals in the camp at the end of the game (if you did all the content available), and it was at least implied that one of them could be repurposed to allow the survivors to go to the city nearby (and work was being done on that front)

Same universe new cast. However it has been said that the old cast can and or will make an appearance.