Full HD or WWHD

Simply open Android's Power Saving mode >> change screen resolution. At the bottom, the amount of time until the battery dies will change.

I'm not sure how accurate Samsung's measurements are, but if true, only a 21-minute difference would be pretty cool.
I guess the best way to judge would be to compare battery consumption after three days each on the different resolutions.
 
Max resolution since I haven't seen significance difference in battery life for my use.
 
+HD still saves me the most battery when I set it to +HD on Med Power Saving mode. And then WQHD saves me the least amount of time.
 
To solve the problem, just restart your mobile after applying wqhd or re adjust the keyboard size
Restarting does nothing, and adjusting the size isn't a big help because it just squishes things instead of resizing properly. Looks horrible and spacing between letters gets a bit weird.