Nix, flox, and containers are best when used together.
Best seems to be when you can transition between various representations smoothly and intuitively; between iterative development, isolated builds, containers, deployment and so on. The design difficulty is how to craft a good user experience along the way.
We're always looking for better ways to tell this story; what would be a good way to demonstrate this value? what is a quick demo that would convey the message?