It's always good to hear one of my guesses was right
As to the extended driver, there isn't any real issue with using it and turning off the kepub options. For me, the biggest issue would be remembering why I had it in six months time. And part of the reason I asked is that there are some people out there that say you must install the extended driver and say it in such a way that implies calibre will not work with Kobo device without it.