Exadata RMAN vs. Non-Exadata RMAN - any differences?
There are no architecture differences in RMAN itself.  The difference is in the speed of the backups if written to the Exadata on-board storage.  So the advantages that Exadata brings in terms of hardware would also translate to advantages in backup speed and MTR (mean time to recovery).  But none of those advantages are the result of changes to RMAN.