I'm no expert, but...

As long as your screen resolution and brightness levels are ok, and your font size is big enough, I don't think you'll gain much from a more expensive monitor.

Depending on what you are doing with your screens, you could look into E-ink (like the Amazon Kindle). Good for office work like spreadsheets and word processing etc. and websites like this one. Bad for videos and gaming. I don't know what might be available like that, but here is an example $$$$ amazon, and a review youtube.

I think a lot of the eyestrain problem comes from staring at something too close for too long.  A bigger screen farther away may help.  I have a 65" 4k tv hooked to a desktop pc and I sit 8' away.  I can stare at this all day and feel alot better than if I stare at my phone or tablet for an hour.  However, your wife may find you less attractive when she sees you parked your la-z-boy in the middle of the living room so you can comfortably read agtalk.  Perhaps this is why I'm still single...

Every half hour look away from the screen and stare out the window for 5 minutes.