Hey, you should mention GSAM battery monitor for Android to get insight into exactly how much power each app consumes. It also gives you an overall real-time “measured” rate of consumption, which you can work towards lowering using the various methods you suggest.
Also may be worthwhile noting that regarding the background “phone-home” communications you mention, for Android -> the best method I found to discern which apps are the biggest offenders is to install something like “NoRoot Firewall” by Grey Shirts. It’s log shows you all background communications.