This could work for casual FPS games, but for competitive FPS gaming like Counter-Strike or Valorant, 20ms is a deal breaker for players who want to perform at a high level.

Pro FPS players consistently choose monitors with the highest refresh rates available.

This informal experiment is quite convincing

Does High FPS make you a better gamer?: https://www.youtube.com/watch?v=OX31kZbAXsA

A 60hz refresh rate corresponds to 16.67 milliseconds frame time, and a 240hz rate corresponds to 4.2 milliseconds.

The issue here is not reaction time, but "feel". Even a moderately skilled player can test this for themselves by switching between refresh rates. Specifically the "feel" is the relationship between moving the mouse and the shift of perspective on the screen. Low refresh rates cause players to over correct their aim as the gaps between frames are larger, and the motion on the screen is less smooth.