It just uses Python and the Blender Python API, so it should work everywhere.

Either from the sidebar like all other addons, or from PowerSave's popover panel in the 3D view.

You can open a .powerbackup archive using 7-Zip, and from there extract the userpref.blend file.

Then you copy paste that into C:\Users\USERNAME\AppData\Roaming\Blender Foundation\Blender\VERSION\config\

This path will only work for Windows, but it's easy to find online what the path should be for Linux or Mac.

These are not part of preferences, but stored inside your startup file.

To see them after restoring a backup, start a new file.

Lights stored in preferences, such as HDRIs for Material Preview or Matcaps, are not currently saved or loaded, because I ran into strange errors with them.

Quick Favorites are not saved or loaded either unfortunately, because they're not accessible from the API, so there's nothing I can do.