JetPack runs on a Linux desktop PC, specifically one with Ubuntu. This acts as a GUI front end to flash software and to software packages. Flash is only of the Jetson of course, but package installs can be selected to go to both the host PC and to the Jetson. Host PC could get items such as CUDA, the nsight edition of eclipse, cross compile tools, so on. You would simply deselect flash and you’d be able to add or remove packages at any time you choose. One of the reasons JetPack is useful is due to the automatic dependency resolution.
If you choose to do this, then you need the micro-B USB connected to the host PC for flash operations (with the Jetson in recovery mode). If you are adding packages you will instead need the wired ethernet (you can choose flash and package install…in which case it flashes over USB, and then the flashed Jetson reboots and package installs go over ethernet).
The most recent JetPack for a TX2 is JetPack3.3. This would flash L4T R28.2.1. See: