Q-4's had both road pilots and switching pilots although all 135 were built with road pilots as I recall. I do not believe that the use of the auxiliary tenders depended upon which regular tender was used.
I see that you are a member of the BSME. Perhaps you can have Doug A. introduce you at some point. I live above Baltimore and know Doug well. I have some knowledge of the B&O from steam days as I saw a lot of Q-4's running.