Why not install nvm via Homebrew? Then install the version you want with nvm. Just a thought.
If you like oh-my-zsh, check out zplug or other zsh package managers. Oh-my-zsh is great (I use it too), but there are many more interesting plugins worth checking out.
Another suggestion is to keep a .dotfiles folder somewhere in your cloud storage (I just use iCloud documents) for all of your config files. If you symlink your various config files to that folder, you can keep all of your machine configs synchronized. It’s very handy!
But yeah, good idea to write all of this down for yourself and for others that might find it useful!