Photoshop still could be used in modern texturing pipline as a texture mixer / compositor. You can do action/script that could make one click 'height blend' masks stack and keep normal,roughness, depth 'channels' inside switchable smart objects and layer compositions . With a bit of java scripting you can automate the…
Saving, editing and manipulating channels is not an issue in Affinity Photo. It's imo actually more convenient there . You don't have to do channel packing scripts or copy /paste to channels manually. It all works through layer system where you can set what goes to what channel directly. There is an issue with importing…
Hmmm, Krita is too far on the painting side of things for me, not enough photo-manipulation to be a good choice for textures other than perhaps stylized ones. I also don't remember it as fast nor very stable. Not checked out most recent major revision though. Affinity IMO are first and foremost Mac applications - not sure…