The query filters available for loading existing users include:
Org Unit Path
Last Login Time
These provide a powerful combination user querying options not easily available via the Google Workspace Admin Panel, however for even more filtering power, the "More Filters" button explains how to use native Sheets filters on your import.
Checking the "Include group membership" box will populate an additional Current group membership column listing all domain groups each user is a member of. Note that for performance reasons, a maximum of 100 groups will return for each user.