Recently upgraded a laptop that had been on the shelf for 5 years up to latest version. Flawless one-step upgrade! nixos. Things never get in a tangle where installing and uninstalling packages leaves random artifacts behind. If you saved it to version control, you can return to a past system configuration and the only thing different is your home directory data.
And yes, if you have a home partition and root partition, that's exactly what you can do. That's the beauty of that approach. But back it up!