I optimize for maximum amount of natural sunlight hitting my retina throughout the day, as that tends to have positive effects on my psychological wellbeing.

So I've set up my desk at a 45° angle bridging a corner of my office where I have windows along one of the walls (with me looking at the corner, of course, not into the room).

So, I'm as close to the windows as possible and have a wall of windows with natural light hitting my eyes from a 45° angle. This is important on overcast days which, where I live, is most of them because otherwise, I would get barely any natural light at all.

With dark mode, this setup runs into trouble on sunny days because sunny spots in the room tend to reflect off the screen, producing glare. This leads me to start drawing blinds and almost always spirals into me sitting in a dark room on the sunniest of days when I most want to enjoy the sun.

With light mode, I can get away with regulating the light through a movable paravent that moves with the sun and takes care of the worst of sunny spots reflecting off my screen and maybe drawing the blinds only partially.