GmsCore as user app vs system app

What microG functionality does or does not require the components (GmsCore, GSFproxy, microG Companion) to be installed as system apps or possess privileged permissions in order to work properly?

Now that we have a native LOS implemention supporting microG signature spoofing even on user apps, and a future special implementation of microG running as a user app for providing services to FOSS apps without a full microG installation, I think the time has come to clarify this matter.

As far as I know, components requiring systemizing include:

• NLP/geolocation data provider
• Internal NLP functions to avoid battery-management process-killng by ROMs
• Ability to use the GmsCore utility to grant reserved permissions to other microG components

Components that use special/restricted permissions include:

• Geolocation (background location)
• SMS retriever

Can someone set me straight on this?

Thanks

No files, tests, or entry points are named. Begin by inventorying GmsCore, GSFproxy, and microG Companion, then verify which listed functionality depends on system-app status, privileged permissions, or restricted permissions; done means documenting the requirements and exceptions clearly for each component.