How to use the user flavour

[oSumAtrIX]

As I understand, the user flavor of GmsCore uses a different package name so that a user can install it following an existing installation of GMS. Applications can then use the libraries instead of relying on Google and their services.

From my experience, GmsCore was conflicting with GMS when installed side by side with a different package name, so my question is, does the user flavor handle such cases? In the past, GmsCore has also allowed package signatures, such as those of Google. Does the user flavor turn that off? Say I want to access libraries only intended for Google apps.

GmsCore now also has a package override feature. When should the request to override be made? On first launch?