Your best bet for a GUI configuration is to use the Bridge network, which creates an internal subnet for your dockers and allows port mapping from the UNRAID server's IP address to specific dockers. It works great, the only downside is sharing the server's native IP might lead to port number conflicts. You can work around that by using non-standard port numbers, such as 8443 instead of 443, but that can get annoying.
If you don't mind dipping into the command line, you can create your own custom docker network using the bridge driver, which will work the same as above, but allows you to bind the docker network with a different local IP address; meaning your dockers could use a different LAN IP address than your server, which sounds like what you are looking for.
