It depends. What is your definition of "security"? There's lots of dimensions of security in the web serving space. If you list out your requirements and specify your threat model, then answers become a lot clearer.
But yes, in general: Caddy's one-liner is a safe way to serve static files in the sense that remote services can't upload files or escape memory bounds to run arbitrary code. It encrypts your connections for you, so they're basically safe from surveillance and modification.
The elements you're describing are all external factors that have nothing to do with serving static files specifically. For example, a reverse proxy just multiplexes requests coming in on a port to various backends, maybe making modifications along the way. Authentication will restrict access to only allowed users, if that's something you require. Containers are more a way of administering a system or mitigating very specific risks that have niche relevance with static Go programs; and VLANs are just ways of isolating network traffic, but again it's somewhat orthogonal to file serving.
Overall, `caddy file-server` is better than Python's simple HTTP server in every way, though: static binary, faster performing, production-ready (handles Range requests properly, and a few other details), automatic HTTPS, folder indices, etc...