We have successfully exported configuration and application data from our 5.3 frontend (RAR only - we do not use CUP or ERM and SPM is only configured on the backend).
We have successfully exported SPM config and application data from 2 sandbox (ECC and SRM).
We have put these 3 pieces in 3 separate directories: FrontendABC (RAR), BackendABC120 (SPM ECC), BackendXYZ500 (SPM SRM).
Please let me know if I need to clarify my questions. Any feedback or tips on the Migration Import process would be great!