Thank you for your interest in the app. Sorry for the late response – I did not see your post.
For now, I suggest leaving your library in Aperture. You can use RAW Power 2.0 as a file browser or as a Photos extension (editing one image at a time) and get used to the app and its features.
RAW Power 3.0 will have support for Photos libraries (using macOS Catalina), so you will be able to use it as an alternative interface to your library. It will not have the exact same features as Photos (each will have unique features). At that point, it might make sense to move from Aperture to Photos.
I hope that helps. You can email email@example.com if you have more questions (or reply on this thread).