Mike, the best I can determine is that the Izotope installers are 32 bit but the plugins are 64 and that is what I have determined on my machine via the “64 bit” app. But beyond that are the security issues with Catalina that might compromise even apps that are 64 ready. And Izotope continues to say don’t upgrade and they haven’t changed their statement in two weeks.
I'm using my Izotope plugins in Digital Performer over Catalina on my MBP without problem. I'm moving to iLok (as much as I dislike having a plastic dongle hanging onto my laptop ). I've not tried their Product Portal manager since the plugs still work without it.
The 2012 MBP is a test machine for now—I have to spend $1K–$1,500 before my work machine is ready.