if you only have 60hz monitor having more than 60 fps will make the game still feel smoother and easier to aim in fps games you will notice a difference
Your monitor frequency doesn't affect your FPS, however if your FPS is higher than your frequency, you won't benefit from the FPS. Your frequency is essentially the cap, above which you can't see a difference. 120fps on a 60hz monitor will look like 60fps. 120fps on a 120hz monitor will look like 120fps.
