Further reading: Which Bethesda games aren’t on Xbox Game Pass and why? The standard Xbox One X 2160p mode has a strange variability to its frame rate on Series X, sneaking above and below the 30fps target. So how should you play Fallout 4? What’s the best version? Well, that’s really for you to decide, but it’s a choice between Microsoft’s FPS Boost at the sacrifice of some image clarity, or a 60fps Xbox Series X|S mod, if you accept that it will dip from 60fps at times. Now that Microsoft owns Bethesda though, there’s always the possibility that they patch both games with bespoke Series X and Series S graphics settings.
Bethesda’s RPG game engines are, let’s just say, notoriously clunky, and the most recent games using it aren’t quite playing nice. Our best guess is that it’s these rough edges to Fallout 4, and by extension to Fallout 76, that have forced Microsoft into this compromise with FPS Boost. Fallout 4 60fps mods give us a clue why FPS Boost is compromised.