I have always been exposed to windows active directory with server controlled logins, server based “home” directories, etc. With the nature of NixOS it seems like it might be easy to deploy something similar by just setting up the configuration.nix as some sort of symlink to one stored on a central server. The only issue would possibly be how to not create home directories on the local machine and instead store them on server. You might be able to make a central passwd file that gets read, but i am not sure just how secure that would be. Thoughts?
You are looking for an old style mainframe, NixOS is about configuration and programs installed.
Depending on your need you can achieve what you want with just some ssh connections and stuff, you can even tunnel a graphical interface!
However if you are just looking for file sharing and syncing, you can just make and http or ftp (tho this protocol is not recommended anymore) and access it across several computers.
You can also use auto-sync processes (IIRC “rsync” is one) or just a syncing daemon and a git repo.
NixOS can help you, but only on the way you apply a configuration. I personally just have my own setup file in github.