Do you mean networking between them? There's two ways of networking between containers. One of them is to create a custom network for a set of containers that you want to connect between each other. Then you can access other containers in that network using their name and port number like so

container_name:1234

Note: DNS is disabled in the default network by default so you can't access other containers by their name if using it. You need to create a new network for it to work.

Another way is to group them together with a pod. Then you can access other services in that same pod using localhost like so

localhost:1234

Personally in my current setup I'm using both pods and seperate networks for each of them. The reason is I use traefik and I don't want all of my containers in a single network along with traefik. So I just made a seperate network for each of my pods and give traefik access to that network. As an example here's my komga setup:

I have komga and komf running in a single pod with a network called komga assigned to the pod. So now I can communicate between komga and komf using localhost. I also added traefik to the komga network so that I can reverse proxy my komga instance.

Yes, you can easily do that. Set the container name and make them on the same network. Used caddy and whole bunch of Selfhostable services with it and I reverse proxy as

container_name:port