The two sides are peers when it comes to connection establishment, but once you have a connection they can and frequently will have different roles.

Many existing iroh protocols have clear client and server roles once the connection is established. E.g. gossip is a peer to peer protocol, blobs is a client server protocol in that one side provides data and the other requests it.

For a client you can use an ephemeral node id and not publish your info to discovery, since you will never be dialed yourself.

It just makes a connection between two sides. How you use it (e.g. client makes a request, server responds) is up to you. So yes.