2) Limited branching: player´s choices or other actions have a small impact on the narrative: you can skip fight, get an different item, some side quests have different outcomes (and then all character involved disappear from the game), but there aren't any over lasting effects on the plot.
3) True branching: the game have ROUTES. Routes are common in Visual Novels, but uncommon in rpgs. Basically, the game narrative can split and there are unique quests, dialogues, enemies and companions to each route. Events and important character outcomes change dramatically depending on the route taken.
It seems to me that BG3 is aiming for a mix of those two. I don't think there will be whole unique locations (like Witcher2) but that your interactions with characters can change depending on question progression you choose. There are quests and NPCs you will never get to talk to due to your actions.
