Hello Symon,
I am a Product Manager at Oracle for "Oracle Optimized Solutions" and particularly the Oracle Optimized Solution for SAP. I am currently working with a team of engineers and we are testing and documenting the Best Practices for Migrating SAP Systems to Oracle Infrastructure.
As part of this effort, we are already published a couple of articles on the topic and one of the articles coming in the near future (I cannot commit to a date) is focusing on migrating an Oracle Database using "Oracle RMAN Cross-Platform BACKUP and RESTORE" and should directly answer most of your questions. I will try to post a link here once the article is published but you should also keep an eye on the article page if you can.
Best Regards,
Pierre