Way I see it the only reasons to use docker on nixos is if:
you need many instances of the same service running on the same hw for some reason
you're trying to run a service that's only packaged as a docker image
That said using nixos inside a docker container is an appealing proposition in that you get all the usual advantages of nix but can run it anywhere you can run docker images
I'd definitely use it (and I do) for deploying remote software and for the use cases you mentioned. Still, we can all agree that, in the context of Nixos, native derivations are superior and almost always preferred. I am currently using a flatpak of zen-browser until the derivations can get added to nixpkgs. But that's just a temporary patch that I will remove soon. I have also seen containers outperform Nix in software that strictly enforces the FHS style and doesn't play nicely in the immutable world.