Just for clarity Access Levels control what a user can see in the frontend, Permissions define what members of a User Group (UG) can do, eg Download, Edit, etc. Obviously if you cannot see something then you cannot take any action!
In Permissions all USER Groups are a member through inheritance of the Public UG but not of the Guest UG. Suppose we have two UGs called Downloader and Downloader_Plus. The parent of Downloader is Registered and the parent of Downloader_plus is Downloader.
So Downloader belongs to UGs Downloader, Registered and Public. Downloader_plus is also members of those UGs as well as Downloader_plus
You can create multiple UGs with Public as their Parent. Also Multipe Downloader UGs with Registered as their parent.
Then you just set a user to be a member of the correct set of UGs.
When it comes to jD content you could also look at the Hide functionality as described in the Advanced section of the jD System plugin.
And in jD 39 you can use the 'Single User Access' feature where ony a named user can see Downloadshttps://www.jdownloads.net/documentation-for-v3-9/access-user-group-permissions-v3-9/single-user-access
PS never use Deny permission