I think it does depend a lot because my aging eyes, even high-DPI OLED screens tire me right out. E-Ink, on the other hand, requires much less strain as my eyes only have to take in the ambient light and not be staring directly into a high-nit source.
I normally set the brightness of displays so that they are similar to the brightness of the environment (which is the general recommendation for ergonomics). Similar to how bright a piece of white paper would appear in that environment. I’m thus usually not “staring directly into a high-nit source”, regardless of the display technology.
The problem with e-ink is that their “white” is light gray instead of white, and their “black” is gray instead of black.