The latest fast ring update includes a "Battery Usage by App" feature that you can view individual App's power consumption. If you see something unexpectedly high.
Say, the new "Microsoft Remote Desktop" App report 14% usage consumption when "In use" (that means I use this App a lot) and 0% in "Background" (that means even if the App default to keep running in background after closing, it's okay to leave it running there without much problem even if I'm not long-press the back button to kill it)
EDIT: Err... it seems there is no longer an option to block Apps from keep running in background anymore. :O