Hi MEB,
Actually Photoshop's Camera Raw allows you to do all that you have listed: save presets, export XMP and reapply the same adjustments to different files, as well as automatically saving those adjustments on opening the file and reading them when you open the same Raw file again.
The problem with iPad is that if the app crashes you loose all you work (it just happened to me, half an hour of adjustments in Develop persona with multiple brush layers). It's very frustrating as you have to start from the beginning and there's no guarantee it won't crash again.
Ilililililiil got a reaction from Jowday in Affinity photo: Divide blending mode