Also, installing SSL Packet Capture showed me that some of my (not even considered shady) apps made a lot of things in the background, eg sending stats or other data to their mothership.
What did do the thing for me was to go into battery settings and set the device in the lowest mode, that severely restricts background work. This, plus airplane, and the device basically doesn't drop anything over a night.
I miss some option (non-root since I want to be able to use bank apps) to tell my phone to never allow anything from apps A, B, and C unless it is active and/or in foreground.
Sorry if I sound like a broken record but to me run at boot, run in background, storage (outside your own not-shared-with-other-third-party-apps sandbox), and network should all be explicitly opt-in.