Is extreme battery saving possible on Android? What is the most extreme battery saver method out there? I don't need anything (location, data, nothing) except phone calls when my screen is off. I know of greenify but even that's not good enough

I basically want to turn my android phone into a Nokia 3310 as soon as the screen turns off?

This is not just a question about app suggestion. I'm wondering if it's even possible on android. Google play services would probably not allow this sort of thing.

PS: I have a OnePlus 3 running Nougat.
If you're rooted and using greenify then there's this option of aggressive doze. Once try it and if not greenify then use kernel Adiutor to tweak your processor as per your need.