Hibernation has always been a fine line. Personally, I have locked down my Nexus 6 and it has been great. You can set certain Wi-Fi networks to act like Cellular when it comes to "restricting data", which prompts alerts if an app wants to do a large download, use Data Saver mode (prevents some apps from downloading/uploading in the background, you can unrestrict specfic apps manually), keep Wi-Fi on/off during sleep (consider setting to off), disabling push notifications, setting e-mail retrieval to manual, restricting auto-sync for photos, videos, music, books and certain Google Play store apps that like to sync to Drive.
Thanks
Amanda