Primavera Superuser and "Update Existing" for Import: Questions remain unanswered from last post

P6 EPPM (license includes P6 Professional client), v 18.8

Users demanding "Update Existing" functionality when importing Xer using P6 Pro, getting error message: P6 error "you must have project superuser privileges in order to perform a project level import"

Apparently to "update existing" during import of Xer with v18, Project Superuser profile is required. Much research later!!!:

Project Superuser is a default profile that cannot be altered to remove privileges!

Questions:

Does the Project Superuser have Global privileges? How to ensure Project Superuser does not have Global privileges? Is Project Superuser restricted to project access granted, or can using this profile permissions affect other projects and global data?