I often make use of photo merge; and my laptop is borderline in terms of power to accomplish this (Windows with Intel I7 8750H 2.2GHz with SSD).
So, Lr basically becomes almost unresponsive once I have a large merge processing, or even two smaller ones. At this point the merge preview is not able to run.
The idea, is to make any merge processing a much lower priority and cap the max number of background processes allowing me to continue going through images and building merge previews....
Tim
AdChoices