Check reviews of the iPhones at notebookcheck.com.
They do a superb job of analyzing the tech details, especially the screens. They are one of the few sites to routinely measure and report on PWM — pulse width modulation — which is how many manufacturers and displays handle changing brightness levels. They literally quickly turn the screen on and off — which produces flickering that *some* people are quite sensitive to. That often affects OLED screens. Other displays, e.g., LCD, change the voltage to dim the screen, so there is no flickering — and no headaches or eye strain.
According to notebookcheck, the 2020 iPhone SE has NO PWM, while the 13 mini has some, but at a high enough frequency that most users should not be bothered.
See
We are testing the Apple iPhone SE 2, which is equipped with a fast A13 Bionic chipset, weighs less than 150 grams and reaches decent battery runtimes despite its small battery.
www.notebookcheck.net
and
We review the Apple iPhone 13 mini with the Apple A15 Bionic SoC, 4 GB of RAM, and 128 GB of internal storage.
www.notebookcheck.net
Here's their blurb explaining PWM.
“To dim the screen, some notebooks will simply cycle the backlight on and off in rapid succession - a method called Pulse Width Modulation (PWM) . This cycling frequency should ideally be undetectable to the human eye. If said frequency is too low, users with sensitive eyes may experience strain or headaches or even notice the flickering altogether.”