It seems a little strange to me to have a functional package manager, but an imperative package install process. I think there are a few projects like NixUP and home-manager that are looking to address this, but I'm hoping Nix will provide an official way to do it.
They recently got a fair bit of interest on the mailing list https://goo.gl/kvNwC1 and raised some money for it as well https://github.com/NixOS/nixpkgs/pull/9250#issuecomment-3208....
I'm pretty sure I read somewhere that it's planned to go in the next release.
I basically define a custom meta-package with all the packages I want as dependencies and install it with `nix-env -iA`.
[0]: https://github.com/asymmetric/dotfiles/blob/master/config.ni...
And as you can see you can also override their config.
I don't know how to list installed packages, as I almost never feel like I need to know that (but if you find out how, I'd be happy to know!)