eyestrainsolutions Most new screens do pwm with 5.000-20.000hz, mostly to trick the eye to think there is no flicker. The frequency itself is hardcoded into the monitor settings. I dont think it is easy to make your own pwm frequencies. You might be able to try an old LED TV(usually 60-120 hz PWM) or a used non-LED TN-Panel. Other than that, it is really hard to know which frequency is used without measuring it.
I did start making measurements of my devices i own, but i think the relative peaks are my problem, not the frequencies. My BenQ has a frequency of roughly 9500 hz when on a setting higher than 50%. Below that it is faster, up to 15.000hz.
Perhaps there is a medical device for that. For testing purposes? Maybe?
But keep us informed, would be nice to know, what frequencies benefit you.