Fallout the Show doesn’t follow any of the games because it’s an entirely new story told in that same universe. The games and show all share the same timeline, and yet each game (including the show) has an entirely different story, taking place at a different location and point in time, in each installment.

So there’s really nothing for the show to follow, other than the established rules of the world it inhabits, and imo it does a very good job of that.