I have had the iPhone 13, 15 and 15 Pro for 1 week now. Here are my findings.
Settings: auto brightness off, wpc off, nigh shift on all day and night, brightness manually adjust to my liking between 75% - 100% depending on the environment. promotion off on iPhone 15 pro.
I browsed reddit daily for hours and face time calls lasting over 2 hours daily so they were all used well daily.
iPhone 13 caused nausea over the course of 2 days
iPhone 15 caused burning eyes over the course of 2 days
iPhone 15 Pro caused nausea on day 1 and then completely fine on 2 and onward.
So my suggestion is the iPhone 15 Pro and see if symptoms subside in the next day or two.
View attachment 2289026