Netrunner is built on top of the Manjaro base.
We already use the Manjaro mirrors for everything, with the exception of Netrunner specific packages.
For these we added a stand alone, and completely separate, repository at the end of the pacman.conf file.
We do modify grub with our own theme, and use our own release file for branding, etc.
However, your still in every other way imaginable running on a Manjaro system.
Note: I will be creating a tutorial soon on how to remove our Netrunner branding, themeing, settings, repository, and other packages, and replace them with the upstream Manjaro equivalents where available and applicable. Please be patient as I go through what steps are needed to make this as simple a process as possible.