Kirk - sorry for being technically stupid here, but how do I check this?
With the "Activity Monitor" application. It's in the Utilities folder in your Applications folder. Launch it and it should show a window listing all of the processes running on your system. Across the top of the window are a set of tabs. One is labeled "Memory". Click on it. Now the memory usage of all processes is listed. In the upper right corner of the window is a search field. Type "Photo" into it (without the quotes). Now only Photo Mechanic, Photoshop, etc. will be listed. There are other processes that Photo Mechanic Plus uses, and they're called "pm-task". In the search field, type "pm" into it and you should now see a few (4) pm-task processes running.
Make a note of how much memory Photo Mechanic Plus and the pm-task processes are using. Check on them when you switch back to Photo Mechanic Plus and experience the 'beach ball'. Do they have a lot of "Compressed Mem", also make a note of the display at the bottom of the window (Memory Pressure) and the various fields next to it. Take screenshots if you can and post them here if your unsure as to whether your system is overloaded. I'll interpret for you.
Use the 'Attachments and other options' link when you're composing your reply to this message and there you'll be able to upload your JPEG format screenshots.
Thanks,
-Kirk