UPDATE, MAY 2021:
The below mentioned tweaks do not fix the eyes/nerves issues. I've tested it thoroughly. Mac Mini M1 does have something evil on board. Probably, it has something to do with GPU, because when in Recovery mode, there seem to be no symptoms. Nothing helps, mates. Windows setup for the same monitors (2 different FHD) works great and is a sharp and immediate contrast to M1 pains. DO NOT BUY CURRENT M1 IF YOU HAVE SENSITIVE EYES OR NERVOUS SYSTEM.
EDIT: Disabled font smoothing (4.) -- looks much better!
I didn't know my eyes were sensitive before I bought Mac mini M1 and Samsung Galaxy Note 20. The "progress" has clearly gone wrong way.
A little back story. As soon as I got the new Mac mini, I plugged in my old FHD monitor. Possibly, it was too old to support FRC/dithering and stuff. It seemed to work fine, no eye strain, but the text was very blurry. I decided to switch to a higher res monitor. First I bought Benq 2705q, which is a solid 2K monitor with low blue light and flicker-free. It immediately gave me terrible eye strain, headache etc. and besides it didn't scale well (too small). I returned it and bought LG 27UL850 that is a budget 4K deal. It felt just a bit better to the eyes but still basically unusable with standard setup. This is how I discovered the whole topic.
Currently I use the following setup that actually works fine.
- Set maximum brightness to eliminate PWR.
Almost every modern 4K panels boasts flicker-free but I don't trust it anymore. My eyes tell a different story.
- Instal a screen dimmer app to be able to set comfortable brightness on a software level.
Iris app has many options in this regard. Also consider lowering your monitor's default contrast, as I found it can add some strain too.
- Choose another color profile in macOS monitor settings. Currently I use 'Generic RGB profile'. I got this idea from one or two reddit posts where people managed to reduce eye strain this way. I have no idea how exactly FRC/dithering stuff is connected to icc profile but it may be working.
- Disabled font smoothing. UI looks better. Feels more comfortable to read.
This is it for now. Looking for more ideas to enhance my setup. Considering SwitchresX DPI tweaks now.