Is there a way to configure a Jetson TC2 from another Jetson TX2?

After you run JetPack from the x86-based host PC to flash and complete the post-install steps (when JetPack installs packages on the Jetson over SSH), then you are free to connect to the Jetson from other machines (presumably over SSH). Just put both Jetson’s on the same network and login via SSH or map the disk with sshfs, then you can make any configuration changes to the root image remotely.