FWIW, I'm sitting in front of a (rather large, 32") monitor with a rather "scary"
barely above 300Hz PWM frequency, and I'm still alive.
And, no, I don't notice it with the naked (well, myopic & astigmatic ;p) eye. It's readily visible through any half-decent phone camera, as it is on the Forma. Where it also doesn't bother me one bit.
(And neither did I just after switching from my old, no PWM monitor).