With an OLED phone. Moto Edge with flicker prevention.
I put brightness to 100%. I installed Darker and Screen Dimmer. I use Darker for Color Correction where I use a red at level 4. I use Screen Dimmer and Extra Dim to take down the brightness of the screen to my liking. Actually, I could use only Darker, which allows both color correction and dimming the screen aggressively, but so far what I've stated above is having a clear benefit. I will experiment further and refine the best approach.
What this does is keeps flicker to a minimum since the screen is at 100% brightness and it reduces the contrast of the screen, which can be another source of strain.
The color filter in the Darker app really seems to help as well.
https://www.reddit.com/r/PWM_Sensitive/comments/1nq3361/having_some_success_with_oled/