I purchased a 1gb 12.9” pro pretty much on launch day and have been using it for nearly all my editing since then.
Context: I use a 2013 Mac Pro for my main LR catalogue and historically have travelled with a MacBook Pro and then exported the catalogue from that to the the Mac Pro on return to base. I had experimented with versions 1 & 2 of the iPad Pro and found them wanting. I had also, like the OP, got really fed up with the LR subscription model and used a variety (all the usual suspects) of alternatives on both IO and Mac OS. Some of them were really great but it slowly dawned that I was cutting my nose off to spite my face because I have a great deal (70,000 + photos and a LOT of experience) tied up in LR.
So after a great deal of research I then did the following, which works really well for me:
1) On my Mac Pro, I filtered my LR Classic Catalogue to give me every image with 3* or more
2) Exported them all as a catalogue. It came to about 2,500 images.
3) Took out a bigger storage package with LR and then imported all those images into LR CC on my Mac Pro.
4) Allowed the Mac Pro to synchronize all that to the cloud (it took a few days)
5) realised from time to time that there were favourite images that for some reason had not made it across, and discovered that you can export as many new catalogs (and then import them into CC) as you like, as long as they all get different names.
Now what I do is as follows:
1) I purchased a USB C reader that fits into the iPad Pro. This is used for my Nikon Z7 files and it is astonishingly fast. Way, way, waaaay faster than any Mac OS import I have ever seen. Like, about 7-10 70mb files PER SECOND - and much much faster than importing direct from the camera using a USB cable - even one designed especially for that purpose.
2) Import the files into Photos, which is disabled from cloud sync. Once they are there, import them from that into LRCC on the iPad. At this stage you can either delete the files from Photos or if you want belt and braces, leave them there until you are sure everything has synced to LR’s cloud.
3) Do all my preliminary editing on the iPad including the wonderful pencil for local adjustments.
4) Allow, wherever possible, the iPad to upload those to the cloud and sync with my other devices. - or wait until I have the bandwidth for that to happen.
5) Get home days or weeks later and find that my LRCC catalogue on my Mac Pro has all the images, wel edited and ready for viewing on a lower resolution screen (very important) and for any final touches - theoretically these would mainly be about color, but actually he iPad Pro has good color rendition.
So what I have is a fully integrated workflow that lets me work at home, in my studio or on the road in an environment I understand and that respects my historical editing practices and cataloguing, and which is blazingly fast. As a clue, the iPad Pro not only imports more quickly, it also processes and renders more quickly than either my Mac Pro 2013 or my MacBook Pro touchbar.
This has, literally, changed my life. It is almost perfect.
I was SO close to giving up on LR. My advice to everyone is, don’t: take some time to understand how to use LRCC across devices and in conjunction with LR Classic and know that when Photoshop for iPad arrives, this combination will be the single most useful thing you ever had, bar your cameras and lenses themselves.
Controversial but true.
But I still really dislike Adobe ;-)