Hi. I just upgraded to 2019 Ultra pack - lots of download time, etc... Now looking at doing a clean install of MacOS Catalina, and was wondering if I can just copy the entire BIAB folder to an external drive, and then back to the system drive after the OS install, OR if I need to start from scratch.

I've had my MBP for 7 years, runs great, but there's an accumulation of junk from simply upgrading over the years, so I think it's time for clean install.