Every Call of Duty game on PC has the same "problem" when it comes to limiting the FPS: it doesn't seem to respect the value you put on it.
For example: you limit the FPS to 60 but it turns out that it's limited to 62.
Also the FPS affects the game physics (movement speed, fall damage, etc.), that's why you may see players who usually prefer 333 / 250 / 125 FPS.
But it's not the purpose of this repository to explain the differences.
I made the website with Call of Duty 4: Modern Warfare in mind, I say this because in some Call of Duty games you can't limit the FPS or it accepts X as maximum/minimum.