JetPack itself only installs on the PC…it is an installer. Other packages can be put on the Jetson if they were selected (or some to PC as well). Most of the extra packages go into “/usr/local/”, e.g., go there and use ls to see if cuda is there. Default paths may need to be updated if you are building software against that (or the Makefile or other config).
Flash itself never installs the extra software…flash is purely the o/s over USB. Extra software (such as CUDA) is over ethernet after flash finishes. FYI, you can run JetPack at any later date, and with only ethernet connected and flash unchecked, you can add packages (you’ll always need to manually enter the IP address if you have not just flashed).
So the question becomes what you really want installed since JetPack itself is the installer and not the end package. If you are avoiding flashing again, then leave the micro-B USB disconnected (and know that in recovery mode it isn’t possible to reach a normal operating system).