Windows Settings, System, Display, Advanced display settings. You can see the current refresh rate and possibly adjust. Your in-game FPS should never exceed your monitor's refresh rate. You can't see 120 FPS on a monitor that only refreshes 60 times per second (Hz). Don't generate frames you can't see; generate better frames you can see.
Ideally your FPSs and refresh rate should be multiples of each other, examples in Game FPS/OBS FPS/Refresh
60/60/60
60/30/60
60/30/120
120/60/120
120/30/120
Don't do something such as
200/60/144