There are many ways to do many things in nixos

For updates you can do automatic updates

Also, there are many deployment tools, like deploy-rs, morph, colmena, bento. They all have different approaches. Some you use ssh to deploy a remote system. Some just fetch the configuration and autodeploy it.

There are many ways how you can play with this. So you can disable sudo, and deploy with ssh only from some or a specified ip. Or you can keep ssh for root disabled and just deploy home-manager. It’s really a lot, you imagination is the only limit