You need to look for one that is Flicker free. Most lcd backlights use pulsing when they need to dim. So they have a strobing effect.
But you can get flicker free backlit screens that don't use pulsed backlights. My lg24gw27 is flicker free, one reason why I bought it.
Thats what I originally thought, PWM is definitely a factor but its just one aspect, I know a test for PWM, if you wave your hands across the screen and see lines it means there is PWM. I've tried 3 different LED monitors that had no PWM and I still had trouble with them. I like OLED but they dont seem to want to make me a 24 - 27 inch 4K OLED monitor.