New to the whole Nix/NixOS ecosystem, so go easy 
I have already managed to set up my personal laptop using NixOS and started to feel more and more comfortable when working with the configuration.
Now, I was working on a personal project that I was planning to deploy to my Proxmox homelab. Essentially, I want to set up a reverse proxy and several servers hosting different webpages with backends, some of them self-developed, some out of the box. Each on a separate machine, of course.
Before learning about NixOS, I would have probably tried to use Docker, so I would have set up some VMs into a docker cluster, built docker images from my projects, then deployed them using docker-compose, for example.
However, this extra layer of abstraction for Docker seems like the wrong choice here, I essentially want the VMs of Proxmox to be my layer of abstraction.
So, NixOS seems to be the right choice. I build system configurations that reside in the same repositories as the projects, then deploy them to the VMs.
But this is where I hit a wall - how do I do that? Because, setting up a VM with NixOS generates a configuration.nix, but the configuration.nix is where I would put all the configuration of what services I would run, so it should be part of the repository right? So what do I do? Is there some example project that does something like this? Some guide?