Note 4 looks like a coin toss as to how usable it will be. Samsungs older OLED screens were usable thanks to not being as horrible as the new ones when it comes to PWM
I'd look into trying an LG Flex 2 on lollipop 5.1
It's the most powerful phone I've found that I can use for hours on end with 0 eyestrain as long as I keep it on Lollipop. Snapdragon 810 and 5.5" 1080p POLED screen with zero visible flicker at any brightness. Back camera isn't bad, front facing camera is LGs typical sub par bs but it's not unusable. Decent DAC. This thing was a 2015 flagship so it's still holding up.
Also the slight curve of the phone that seems like a gimmick is actually really nice
They are relatively cheap to buy new as they didn't sell so well for some reason and there's a massive stock of unsold ones.