I use a 6 plus which doesn't bother my eyes and a buddy of mine came by who has a XS Max. He let me take a careful look at it- in the dark.
Holy crap the flickering from that OLED screen is atrocious. Clearly visible strobe effect anytime my eyes moved quickly by the screen. Straight on and especially in my peripheral vision. It looked like those horrible flickering tail lights on Cadillac Escalade vehicles.
I literally couldn't allow my eyes to get anywhere close to that flickering piece of garbage, even peripherally. Way too stroby for me.
I asked him if his screen gave him eyestrain or headaches and he said no, yet I couldn't get within two feet of it (in the dark) without it really messing up my eyes.
So for me- Apple's OLED screens are hazardous garbage, yet for others, they're fine. So you've got to try out different screen tech (LCD vs OLED) on your own to see what bothers you and what doesn't.
As your post rightly indicates, not everyone can see or feel the effects from that flicker. My husband can’t. But sadly, I have the same reaction to it as you do.
There’s a possibility, if I’m reading the leaks and rumors correctly, that the upcoming 2019 OLED iPhones will be using the same display as the Note 10. I’m thinking it will be the same as the one on the Note 10+. I have a Note 10+. There is some pwm flicker and I can detect it but it does not seem to be negatively affecting my vision or nervous system...yet. A few days on my XS Max left me bed ridden in a darkened room for a day and unable to speak and reduced control of my hands, due to a form of migraine.
iPhone 8 Plus has the best LCD display I’ve ever seen. Going from an 8 Plus to an Xr display did require a short adjustment period for me. I think the color of the LCD on the Xr is really good. I didn’t like the color on the XS Max display. There was too much change in tint in off axis viewing.
The 2019 iPhones will be the ones to get if they indeed get the same display as the Note 10 phones and if Apple does not tinker with calibration. For a lot of us it is not the typical pwm flicker of OLED that does us in, but a customization Apple applies to “improve” the display to their standards.
The iPhone XR display is perfectly acceptable but I have to be honest and say the 8 Plus display was the easiest on my eyes and I would prefer that display.