[jjd-uk]

Once nodes are created, and categories created, the action on click for the nodes would go to a playlist or video source for that node? 

Yes that is right

I would like to scan library to new content but then my 4k movies end up under the main movie menu. I only want 4k under 4k and the same would go for the TV shows. But I do want everything scanned into videodb.

So collections would show both.
 
I guess I am not sure which to use a playlist or to edit the nodes or both.

Have you added rules to exclude the 4K content to the default Titles and Sets nodes? and then made sure the Menu/Widgets are pointed at these modified nodes.

Then have you create new Titles and Sets child nodes within your 4K Movies parent node to display only the 4K content?