Okay... I removed RM7 per above. Then I installed the beta RM7+wrapper for Catalina because it says it will work on previous OS's. Upon installation, it said an update was available so I installed the update.
I was able to open the rmgc file that I'd created before with the gedcom import.
I went to the source check mark and double clicked. I got the message to install gecko. The beta wrapper instructions said to select install. So I did.
I started to get the dull-thud sound again and things appeared to be frozen. I did see I was able to select Quit RootsMagic from the File menu, so I did.
I got the typical backup or skip message. I skipped. AND THEN instead of quitting, it brought me to the source screen for the source I had previously selected before getting the "install gecko" message.
THEN the screen cleared and I got a small error message box that says: "Access violation at address 00593857 in module 'Rootsmagic.exe'. Read of address 00000010."
Going back in...
P.S. when I clicked OK on that error message, another message appeared briefly about a control window. I didn't catch the exact wording.