Bethesda has update the FAQ for Fallout 76's B.E.T.A. The FAQ updated with the question "Is the B.E.T.A. going to be the full game and will my progress carry over to launch?"
The answer being "Our current plan for the B.E.T.A. is it will be the full game and all your progress is saved for launch. We hope you join us!"
This means you’ll be downloading the entire game for the beta, but you'll also get access to the entire game with it. Any progress you make in the beta will carry over. So you’ll be able to continue where you left off when the game comes out. A date isn’t known for the beta besides just coming this Fall, but the Xbox One will get it first.
Fallout 76 releases on PlayStation 4, Xbox One, and PC on November 14.