"Todd clarified a few things in an interview he did today at E3:
-Fallout 76 cannot be played offline. It is an online only game.
-Even if you choose to play solo, you will see other players. (Presumably they can interact with you if they see you too, even if you don't want them to).
-He confirmed that there are no NPCs in the game. Every human is a player.
-There is no option to "opt-out" of PvP.
-VATS will appear in Fallout 76. We can still pick body parts, but it will be in real time, not slowed time.
-Fallout 76 will support player-made mods.
-There will not be mod support at launch.
-They plan on Fallout 76 having a "private world" option, but not at launch.
-There are more people at Bethesda working on Fallout 76 than any other game in the company's history. He says there will be constant content coming out for the game.