Always check "GPU scaling" before creating a custom res. If your monitor fights the new resolution, let the graphics card handle the heavy lifting. Your monitor won't know the difference, but your frame rate will.
Here’s the trick: You render the game at 4K (3840x2160) but tell your 1080p monitor to display it. The GPU crunches the math, squishes those extra pixels into your screen, and the result is astonishing. Jagged edges vanish. Textures look richer. It is essentially the most expensive, brute-force form of anti-aliasing available. custom resolution
The catch? Your GPU has to work twice as hard. If your card is gasping at 1080p, it will have a heart attack at 4K. If you have ever watched a hardcore iRacing or Assetto Corsa streamer, you might have noticed their screens look... square. They aren't using old monitors; they are using custom resolutions to crop the image. Always check "GPU scaling" before creating a custom res