Setting the GPU to maximum performance works here.
Conflicting GPU Settings: We also came across several instances where the GPU was bottlenecking the game itself because of its power-saving and other settings.
Here, lowering the settings or enabling the Windowed mode helps.
High in-game settings: There are also situations where the in-game settings are set very high and there aren’t enough resources to cater to the requirements.
Here, we can try diagnosing and closing all third-party applications running in the background.
Third-party applications: If there are other applications running in the background which are consuming your resources, Fallout will not get its required computational power and hence, cause lagging in the game.
FPS Limit: There is by default, an FPS limit in Fallout which automatically reduces the maximum number of frames per second which you can achieve in your computer.