When in fullscreen game FPS is capped and performance is worse

For some reason, as the title says, whenever my game is set to fullscreen the FPS is capped at 60 and the game feels like its running slower than that. This is reproduceable on multiple machines. To work around this I came up with my own borderless windowed method. It really would be much more convenient if I could just set the game to fullscreen because on non-standard monitors the window doesn’t cover the whole screen. Please help.