Workspaces licensing model

Workspaces operates a little differently to Citrix - each user is allocated a dedicated Workspaces instance and storage is persisted for that user on that instance for the lifetime of the instance. So you'd create the instance for the user and it is dedicated to them until you terminate the instance. That could be hours or days but generally Workspaces instance are long-lived - they are a permanent desktop for the user.

If you're looking for desktop applications to be delivered to users but you don't need to maintain a permanent desktop for them you might look at AppStream instead. Users can still have persistent storage if they require.

There are a few ways to provide shared storage between users on both Workspaces and AppStream - I'd first look at FSx for Windows.