Greenify

I used it at first but once I uninstalled, my SOT went UP. So it's staying off my G6.
 
Greenify and all the apps like it became unnecessary in 2013 and obsolete when Doze came into existence. Those apps typically suck MORE juice than not having them because they kill processes that have to be running for smooth operation and most apps do better in stasis than they do being restarted constantly.

In theory. Unfortunately we still sometimes need tools like Greenify to tame apps that are not well-behaved.

No one tool works right for all situations. I like greenify but not in non-root mode, so I'm not using it on my G6. For the most part, unlike in 2013, I find myself avoiding poorly-behaved apps on my phone entirely, because without root my options for controlling them is so limited.
 
I just got the Korean hifiDAC G6 and had normalish/poor battery drain. smart doctor told me 3 apps were draining a lot in background - Spotify, Facebook and Komoot. I put greenify on and added them to the kill list and battery has improved massively! Only problem is the always on display is sometimes affected, you get a blank screen for a few seconds as its working things out, not always but enough to be a pain.