Yeah: NixOS Search
You can then use variables from that with $VARNAME.
I’d definitely recommend using networkmanager over raw wpa_supplicant for normal desktop devices; it’s much better at mixing declarative and nondeclarative networks. It’s also more versatile when you want to switch between networks, can easily turn on/off VPN configs, …
The main downside is that you need to write networkmanager profiles, and the file format for that is a bit underdocumented. But it’s ok as long as you don’t want to do anything too complex.