[Darryl Ramm]

Lots of info there except you missed some of the most useful stuff, especially what exact Pro Tools versions you are using on what exact macOS version?

Rule number one of troubleshooting CPU errors is to always suspect plugins.

Are those Omnisphere plugins up to date? Compatible with your macOS and Pro Tools version (note you need Omnisphere 2 for official compatibility with Catalina). And as Ben says, they seem suspects here. (edit: I fixed a typo that said iZotope not Omnisphere)

And you have a UAD system... are you absolutely sure you are not instantiating UAD plugins in a session? No hidden tracks etc. None of those big slow high IO buffer demanding UAD plugins? Hopefully you understand the overhead issues with UAD plugins within Pro Tools.

What troubleshooting have you tried? Lots of standard stuff you need to go thought. Start at "help us help you" up the top of every DUC web page.

You should have tested by removing all .aaxplugin files from the plugin folder (and just testing only with the default Pro Tools plugins that Pro Tools will put back automagically), trash prefs (keep trashing prefs as you try other stuff, use Pete Gates PT Prefs utility), try other sessions, test with Build-in Output, test from a new admin user account, ... there are a pile of things to try and if you should list exactly what you tried if you want useful help.

Is the system fully optimized? every last thing done, WiFi off, Bluetooth off?
Do it all for now, you can back off some of them later.

Uncheck ignore errors (you want to see errors while troubleshooting).
Hopefully you are working at sane sample rates of 96kHz or lower.
Try dynamic plugin processing off.
Set cache size to a few GB.

If your samples would fit on the super-fast internal PCIe/NVMe SSD then that is likely a better place to run them than the external slow glyph drive. Those PCIe/NVMe SSDs are usually capable of running boot, audio sessions, and samples.