User and display groups

I am trying to set a user group that will have access to specific displays (a Display group). I set up a user group, gave it page security permissions. I created a user and assigned it to this user group. I set up a display group and assigned the displays to this display group. I also set the page security to the user (Although I would expect that when he is assigned to a user group it will get by default the page security of the group). When I sign in with this user I see the dashboard and the display menu (As I configured) but I don’t see the displays.

You will need to assign permissions directly to the displays.

Same logic applies for existing layouts/media that your user group should have access.

That’s exactly what it does, there is no need to assign permissions to the group and the user - unless you want that particular user to have more permissions than the group -