The most popular way of configuring containers are by using environment variables that live outside the container. But for apps that use files to store configuration, you can designate directories on your host that will be available inside the container (called “volumes” in Docker land). It’s also possible to link multiple containers together, so you can have a database container running alongside the app.

AFAIK they don’t allow passing content through jellyfin, or running a vpn through a tunnel. General web services are fine tho