The dedicated server has no ui, there is no use in spawning widgets on it. It normally runs in a headless configuration. You can only see the terminal if you run it with the -log command
I was just showing someone the dedicated server in a project demonstrating repNotify. There is a downloadable project with configured client / server. You just need to point the uproject to your compiled engine source to test it.
The project settings let you select the map the server starts on.
If you want a dedicated server then c++ is the only option. It doesn’t work with just blueprints.
As for if you need a separate project for client / server. That’s a tough question. The client needs to call events on the server, so it needs to know about them (their input parameters , is it a reliable RPC etc).
You can’t really do that with 2 separate projects.
The only way you could implement this would be through a custom network protocol or through serializing / de-serializing commands through for instance json (not the most efficient).
A third option would be to have your server logic be a 100% custom, but that is more complex. Then the client and server logic can be completely isolated only pushing information via sockets.