I would like to know the difference, in terms of accessibility, between a full install via download and connecting to the hard drive that the physical program comes on. The reason I ask is because I have a one TB ext drive. If there is an advantage in a full install, I would choose one of my pc's to do away with the HD. Also, does the computer have to first contain basic BIAB files to operate with an ext HD.
The download is the same thing you are getting on the external USB. You can run completely from an external drive if you want with the possible exception of a few files. Here is a thread on this:
https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=303262