Whenever my system is in an incorrect shape, I can not only roll back to a previous one, I can go back several updates ago. But an update on NixOS could be a system package installation or a settings change.
My system settings are all in two files, both in git. There’s also the versions of all of my packages that are installed into the store, each with versioned dependencies, but not globally installed so they don’t conflict with each other. This is why I can have a rolling system using the stable wine version.
I also found out packaging is not so difficult so I’ve actually successfully packaged some of the software I use