Ok, here’s a controversial question:
Is there actually a difference between 60hz and 120hz?
Yes. Competitively, imagine a scenario like this: an enemy is crossing a doorway in front of you, and that takes a tenth of a second. On 60hz, that gives you six frames to react. On 120hz, it gives you double that, 12 frames. Even though it's the same amount of time, a higher frame rate does indeed have an effect. (this can be seen a lot on 30 to 60hz as well. Usually players get better on higher frame rates.)
mostly no, but maybe in games that require extreme reaction times such as first person shooter or rhythm games
I agree that most of the time it’s pretty unneeded/unnoticeable though
yes it's double the amount of Hz (double the amount of potentially displayable frames per second)