Username or EmailPassword
I'm at a Windows machine right now, so I can't answer the first question. I'll check when I get home later tonight.
As for the second question, I believe the Wall Plugin is in the "Desktop" section of the Beryl Settings Manager, right above "Widget Layer". You need to select it before you can activate it (either with Super+e or by assigning a screen corner to it in Shortcuts).
Note that you can't have both the Desktop Cube and the Wall Manager (selecting one will bring up a dialog box asking you if you want to disable the other).