Comment 4 for bug 252664

I don't believe the feature requested here will happen anytime soon. Photos are saved directly from the same stream of the viewfinder, a frame is taken and encoded into a jpeg file. To do what the OP suggested we will need to stop the pipeline, close the device, reopen it with an higher resolution, take a frame, stop the pipeline again and reopen it with the lower resolution.
It will take no less than 3-6 seconds just to shoot a photo. I'd say it's a wontfix.

About refresh issues I believe Neil is talking about some issue we had in the past with gtk double buffering, they should be fixed in git or in the 2.27.3 release expected in the next few days.