Can this app backup/restore RCS messages?

Yes it can, on Samsung phones or if you use Google’s Messages app for messaging.

Google’s Message app now supports RCS messaging with all service providers in USA as well as a lot of providers outside of USA. Messages stores these messages in the SMS/MMS database on the phone as MMS messages and SMS Backup & Restore can backup and restore these messages. If you wish to use RCS messages and backup/restore them using SMS Backup & Restore then we recommend using Google’s Messages app instead of the phone’s built-in messaging app.