Question about Microsoft Office Home & Student 2019 German

Yes you can, because the software has to be downloaded.

PKC = Product Key Crad; you get a key on a card sent to your home.

I would recommend your pure key. Then they can download the corresponding version and install it on a USB stick. Linzengo.ch would be a place to start.
The product key of this version is of course also possible but the installation will not work without a CD drive.