The "sweet spot." It provides a slight boost in FPS and visibility without making the game look too blurry or distorted.
You must also create a Custom Resolution in your GPU control panel (NVIDIA Control Panel or AMD Radeon Software) that matches what you put in the config file, or you'll see black bars. Fortnite Stretched Resolution: Best GameUserSet...
Search (Ctrl+F) for the following lines and change the values to your desired resolution: ResolutionSizeX ResolutionSizeY LastUserConfirmedResolutionSizeX LastUserConfirmedResolutionSizeY The "sweet spot