Just a few things about Appvolumes.. Although i would suggest reading into the manual because it is explained inthere 
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Appstacks can be assigned to both users and computers. If you assign an appstack (read only as you state) to a user it will only be assigned to this user. During login to the machine it is reconfigured and appliactions are assigned. If another user logs in the applications will not be there or you need to assign the applications to both users. During logoff the appstack will be removed form the machine.
That being said. If you use Appvolumes you need to use a non persistent floating pool and refresh a machine to clean state after use. If you want to record user settings use (as Lakshman said) writable volumes.
If you want applications to be installed on a machine for all users to be used (and all settings to be used on that machine) i would suggest not to use appvolumes and go for persistent machines with persona management (or anything like that).
The power of Appvolumes is that you have 1 golden image with a non persistent floating pool and the machine is personilised during login for that specific user.