RDX drives are supported by Acronis Cyber Backup 12.5 and by Acronis Cyber Protect 15 as a backup destination. They are treated as a regular local backup location.
If you are backing up to a shared RDX drive with swapped disks, set up automatic cleanup via a command or script, so that the disk content is erased before backup starts. SeeBacking Up to Removable Devices with Regular Drive Swaps This way each disk will contain one full backup.
(!) Note that rotating removable drives that you use as backup destination must have the same drive letter assigned to them.