how to check background apps the pragmatic way

Time is throughput; background tasks either compound value or leak it. On a red-eye flight, my battery nosedived until I killed a syncer - lesson logged.

Inventory: Open Task Manager/Activity Monitor/System Monitor; sort by CPU, memory, and network.
Classify: Mark each as critical, supportive, or optional.
Decide: Keep, pause, or remove; prefer disabling auto-start to force-quitting loops.
Measure: After changes, recheck battery drain, temps, and wakeups.

Tradeoffs and long-term impact

Hard kills feel fast but can break caching, updates, and notifications. Better: schedule, restrict background data, and audit weekly. Quiet efficiency compounds; expect modest gains - real, durable, controlled.

Related intents: see what apps are running, stop background processes, manage startup programs, reduce battery drain, monitor CPU usage.

https://support.google.com/android/thread/183426834/how-can-i-find-and-close-apps-running-in-background?hl=en
I would like to know how to close them without having to drill down from Settings to Force Stop. If I swipe up halfway to see active apps that I can close,

https://discussions.apple.com/thread/250769915
Go to Settings>General>Background App Refresh and you can see what other apps are allowed to update data in the background. iOS dynamically ...

https://support.google.com/android/answer/9079646?hl=en
From shortcuts - To open Quick Settings, from the top of the screen, swipe down twice. - To see the number of active apps running in the background: At the bottom ...