PG278Q Hz Problem, need help please

[ToastyX]

I don't know what the laptop's hardware can actually handle, but it's behaving like it doesn't support DisplayPort 1.2. That could be a hardware limitation or a driver limitation.

The PG278Q doesn't define 1920x1080 @ 144 Hz as a supported resolution in the EDID, so it's not going to be available if 2560x1440 @ 144 Hz is not available. You could add 1920x1080 @ 144 Hz as a custom resolution, but the PG278Q doesn't have a scaler, so it can't display lower resolutions without GPU scaling.