Backup Server, licensing

Hi, new to Proxmox.

From what I see online, Backup Server provides Incremental & Deduplication, and the built-in/free backup does not?

Does the Remote synchronization feature require a second paid license for the second server?

In our current (not Proxmox) setup we've been using a combination of image backups with incrementals, and rdiff, with rsync for off-site. Are the backup files accessible at a file system level, to rsync off-site?

Thanks,
Steve