So OnePlus X gives me terrible headache and eye strain (worse than Oneplus ONE with IPS screen). I installed original Android 5.1.1, Twilight app, set brightness to 100% and dimmed the display with the app. The specifications of the phone are the same as on Lumia 930, so I assume there is something in screen that gives eye strain. I am not sure what else I could try. These phones are already outdated and they are unusable, so going "back" in time would mean buying only used laggy, unusable phones.
So we are stuck on 2013-2014 without the solution for the future. I think eventually we will need to go back to basics and buy Nokia 3310 (2017 edition). One of my clients are still using old phones, and when asked how do you check emails and everything he says - I don't, I just phone everybody, like on good old days. He is over 60 years old so he is used to it. Not a solution, but more of a bahaviour change. For example amputees cannot walk or write, we cannot look at the new screens and use new devices.