So I understand that after I have installed the Win 7 backup on the unused drive and then do what you call an "upgrade install" using the Win 10 dowload I will wipe the personal data and installed programs from the Win 7 backup.
No. A Upgrade installation allows you to keep intact the files, settings, and programs from your current version of Windows. A Custom install would wipe your data. Of course, you always want to keep a backup just in case.

Like I said, a "Repair" install is doing an upgrade install but you're staying on the same version of Windows. That's why they call it an "In-place Upgrade".