Thanks Mike for the info. I am going to research the OWC Drive Dock to use SSD storage, I am using a 2TB NAS on network at present and it is a pain sometimes (slow to load, etc.). I prefer the APFS volume over the external drive, it is faster in my case. I have created both. Creating the volume was easy, to create the bootable drive with OS Catalina install I used a third party software, still easy to do.