You will find below all of the reason why your users shows a full remote desktop instead of a unique application or remote taskbar / floating panel / application panel. Or the other way around. 

Open an admin tool, click on the server tile, and click on "Session opening preference". 

Make sure that the "All users have full remote desktop" box is not checked. Then go the application tile, click on "Publish application", and select "Remote desktop", make sure that the "Assign this application to all users" is not checked. 

The next move is to check your assigned applications, make sure that no groups have the "Remote desktop" application assigned, if that is the case this application will always have priority over others. 

The last step if none of the above has solved your issue is to manually edit with notepad the AppControl.ini file located in C:\Program Files (x86)\TSplus\UserDesktop\files In the paragraph "Security", make sure that alwaydesktop=no 

You will also be able to check your application assigning settings here, in the example below only the local administrator has access to Microsoft Remote Desktop : 

[App1] appname=Microsoft Remote Desktop