A while back the editor got much slower for me when stitching raw images. I think it used to use jpeg previews, but now the editor decodes the raw files in order to display the images in the window. I often just want to quick pop in and see what the pano would look like with one image disabled, or see how much overlap something has, or change the projection. Now I have to wait a long time. I find I can change the projection and then go back and look at the main groups view to see how it has changed much faster than waiting for the full resolution files to be rendered. I have tried setting the gpu settings to low, but that doesn't seem to affect it.
So I'd suggest in the future that the editor uses the low resolution embedded jpeg previews (or whatever it is using for the main groups window) and then fill in the higher resolution RAW file previews when they are ready.