Thanks for the prompt response Nik.
In regard to point 4, what I do with a shoot of several hundred images for a customer is import full size JPG into Photos, do some minor format changes and export the proofs to the customer to select the required images. Once he has made the selections I then edit the selected JPG images in Photoshop, generally to clean the background and clone out unwanted objects.
When I go back to Photos or Raw Power the image has not changed. If the preview is referenced to the original file (which has changed), why does it not see the changes? In Aperture it just started “Processing” and popped up new after a period of time.
I was able to force it to change though by making a very slight edit and saving.