Question about server/client when launching via editor and a multiplayer inventory

I recently started using UE4 by watching a lot of tutorials (also the networking blueprint tutorial).
There is still one thing I don’t understand. When I start the game via 2 instances (dedicated server off) I get a server and a client screen.
Does the server screen represent the host & player of the listen server (if I would start a listen server ingame) or is it just to check/debug if the server gets all the correct information?

What information is saved on the servers playercontroller then? Do client inputs even work like toggling an UI on the server instance (since they are client only)?

Let’s say I want to create an inventory. I would check for the player input, then check on the server if the pickup (distance or other conditions) is valid, then add the object on both server and client so when the player tries to manipulate the item the original is still stored on the server.
Is this the correct way?
Should I use playerstates or playercontrollers for the network inventory?

Thanks in advance! If all these questions would be answered by a tutorial, a link would be more than helpful for me (since I looked one up but couldn’t find one answering all these questions) :slight_smile: