What would be an ideal ratio of brightness to contrast? I used to have at the same number (85/85) and it gives me headaches. But im aware that making ur screen dark can make ur eyes more tired.

What is the most ideal ratio? Is it having a low brightness but higher contrast so ur screen is not very BRIGHT but you can read stuff? Same level? Or higher brightness but low contrast?

It really depends on the monitor but try the default settings and work yourself from there. If it is an old monitor you may have to crank up the brightness setting. Try 100 for the contrast. I suspect that your eye strain comes from low refresh rates though.