I am using this combination on an iPad Pro (512 GB) and there are some problems. However the biggest problem is that Photoshop reduces the dimensions of the file considerable.
Using a Nikon D810, my Standard Dimensions are 7360 x 2016 Pixel.
After I opened the file with Photoshop Fix (Share-menu, with the function "Edit in") - using the healing function - and "Save & return to Adobe Lightroom" (with the blue bar on top), the Dimensions are 2560 x 1709 Pixel.
Furthermore - I used the Extension *.NEF (Raw on the Nikon) and the new file becomes a *.PNG.
When opening the APP Photoshop Fix separately and fetching the photograph from Lightroom - it lands up to become the following size: 2048 x 1366 Pixel. This also applies if you edit a pic with Photoshop Express on the iPad. (in Photoshop Express you can choose the Image Resize - and I have choosen "Original" - however the APP does not like my idea)
There is no chance to change or setup anything - it's just the way it is.
Anyone any idea on how to handle that ---- PLEEZE !!!