If you're running NixOS there's an impermanence plugin that allows you to specify specific directories and files you need to persist outside of what NixOs/HM builds for you and then use a tmpfs in-memory partition for root and/or home. Then at boot you're loading up the NixOS/HM config and then the persistent files are symlinked or mounted to where they need to be, but otherwise you have a fresh system on each reboot. It's a bit painful and manual to figure out exactly what to keep (unless you just want to keep the entire .config, for instance, which I don't) but it's amazing to know that you can mess up your home directory as much as you want and then it'll automatically clean itself with a reboot.