A few months ago I published an article showing readers how enable Remote Desktops and Remote Apps in the same collection. So when a user logins into RDweb you will see both RemoteApps and Full Desktops.
For information how to configure this please click (here)
After some testing, I have found issues when using User Profile Disks. When a user logs in to a RemoteApp, it will map the user to the user profile disk (UPD) as expected.
If the user starts a new connection (Full Desktop) whist having a RemoteApp open, the user will get a temporary profile and a blank screen as the UPD cannot load. This means that when you launch a RemoteApp, the UPD is locked to that session meaning you cannot load a full blown desktop at the same time. If you want this functionality, you will need multiple collections (one for RemoteApp’s and one for Session Collections).
There are no fixes for this issue at the time of writing !
Ryan Mangan's IT Blog 
Another thing I noticed with this on Server 2012R2 – It used to be possible on 2008R2 to use the SecurityDescriptor registry value to limit the visibility of the Remote Desktop link in RDWA. However, even when this SecurityDescriptor is set manually on 2012R2, it is not obeyed and instead the Remote Desktop link is made available to all users of the Collection.
Hi Ryan,
What would be the best practice to make the UPD highly available ?
I currently defined the location on the first session host, and I am about to add a second session host and assign the same collection (RemoteApps only) to achieve high availability, but if the UPDs are defined in one server and do not replicate – it may be a problem, if SH1 goes down, right ?
I just would like to know if there is a best practice for synching the UPDs on more than one server.
Thanks,
Shimon.