Hi there!
Maybe I don’t manage to consider all of your iPad workflow requirements, but given the storage limitations on most iPad models, you may need to consider storing all of your image assets in iCloud Photo Library. RAW Power 3.0 can access it and also store all the adjustment data there. So you have everything in one place. You would want to subscribe to a 200 GB or 2 TB storage plan (I chose the latter – to cover the whole family at the same time), and latest when your iPad runs out of storage space, you would need to set iCloud Photo Library to optimize storage. As soon as you select images in Photos or you access them straight from RAW Power 3.0, the full res images will download from iCloud.
The one thing that would concern me is that all of your image data now exclusively resides in iCloud. I have an iMac alongside the iPad which I use to keep an archive of all raw files plus edited jpgs, besides having it setup to keep all original full size images in parallel to iCloud Photo Library. Plus of course a whole host of backups of everything.
Maybe you could overcome this issue when using an iPad only by exporting jpgs and raws (haven’t tried the latter) from the iCould Photos Library through the RAW Power export function first into the iPads file system and copy them from there over to an external storage device attached to the iPad. Then delete the local copies from the iPads file system to free up space. For my personal liking, this workflow is too cumbersome.
Another aspect to consider: I find it very hard to use the iPad to produce predictable outcome for printing images, even when setting the screen brightness to a lower level. The iMac with a its display calibrated to 100 cd/m² and properly profiled is much better at that task. It would be even better if RAW Power were to support soft proofing based on output profiles for your targeted output device and output substrate. I filed a feature request for this a while ago.
Hope this helps.
Best regards,
Erik