The latest patch for Fallout 4 changed the location of the frame rate setting for the PlayStation 5, Xbox Series X and Xbox Series S versions. To see how you can access it, you can check out this guide at Seeking Tech.
1. This setting can no longer be accessed from the pause menu. Instead, you need to quit your current session in order to return to the main menu.
2. From there, go to Settings > Display.
3. You should then see Frame Rate Target, which lets you set the FPRS to 30 or 60. If you have a 120 Hz screen, then you should also see an option for 40.
4. Underneath, you should see Prioritize, which lets you prioritize the graphics to either Performance for better frame rate or Visuals for better resolutions and other graphical features.