No, a user cannot use this G Suite Backup tool on Mac OS machine. It is a completely Windows-oriented tool.
Yes, Outlook installation is necessary to perform Google Apps to Outlook migration..
Yes, the G Suite Backup Tool does not compromise folder hierarchy even after downloading data on the local machine.
Yes, Google Apps backup tool requires user to add username and password of single or domain user account to backup G Suite data.
Yes, a user can filter the data for downloading. One just needs to specify the name in comma-separated value, the Google Apps Backup Software will backup that folder only.