A) Is it better (faster) to get a message using the GetMessage( <id> ) function at Account level or by using the SelectedFolder.Messages( <id> ) function.
I will recommend to use the Account.GetMessage(MessageID) method instead of Folder.Messages(MessageID). I did a simple test of these two methods. GetMessage() method retrieve the message faster then Folder.Messages(). In my test the GetMessage() took .00350285 Milliseconds where the Folder.Messages took .26625061 Milliseconds.
C) Is it possible to integrate my Applets with the toolbar in the QuickViewer. They get the standard Reply/Forward buttons but not my additional ones.
Try the GroupWise Main Window Toolbar integrations.
Hope this helps.