The more fps you have in-game, the lower your input lag - regardless of what your monitor’s maximum refresh rate is. That is a fact.
The issue is, when your framerate is higher (or lower) then your monitors refresh rate - you are likely to notice screen tearing. Many players would rather prefer to have little to no screen tearing and keeping their in-game fps limited to their monitor’s max hertz, then to have the advantage of a bit lower amount of input lag at 300 fps. When you have a monitor that is 144hz or higher, screen tearing is much less noticeable. So many players just play at 300 fps and are not bothered. But in your case on a laptop with 60hz, it will probably get ugly playing uncapped.