Install client on another machine with digital version only?

[Zaft]

You could just back up all the FFXIV files on a USB drive and then copy it into the proper area on your other machine. I did this to install FFXIV on my gf's PC. You just won't have any shortcuts in the start menu, but everything works fine.

This will work. If you want to add the shortcuts in the start menu, you can do so by navigating to this directory:
C:\Users\MYNAME\AppData\Roaming\Microsoft\Windows\Start Menu

Where MYNAME is your user name (so, for example, Zaft).