Response
You can find a summary of the changes from RC7M to the RC8 controller listed at the link below. This summary includes both hardware and software changes.
https://www.fa-manuals.denso-wave.com/en/usermanuals/001076/
You can find specific programming command comparisons at the link below:
https://www.fa-manuals.denso-wave.com/en/usermanuals/000513/