How does degoogling affect battery? Google apps especially play services show on top in RAM consumption and always have few processes running. Also these apps are very bulky.

By degoogling I mean disabling GSF &amp; Google play services. But is there some sort of push service-like stuff that can be done more efficiently with GSF? (Considering a person is very likely to use Whatsapp, telegram, Facebook, instagram, reddit etc.. even after disabling these google stuff). Do anyone have micro benchmarks on these?
You can run Google free device, however you really have to know what you are doing.
Removing Google apps and services from an existing device isn't a recommended way. You may run into serious problems. The common way to get a Google free device is installing a custom ROM without Google apps (for license reasons most custom ROMS don't include Google services/apps).

If you disable GSF apps will loose the push notification service (if they still run at all). For a large number of apps GSF is a requirement.

Some apps have an alternative custom push system implemented but now every app has to run it's own background service. For example signal has such a service but the authors warn that it causes "reduced reliability or performance" and as every app has to open an own connection to listen for messages the overall power consumption increases.