Re: When do you teach your personal style?
Are we talking about teaching style, or style of aikido?
I think everyone starts to develop a personal teaching style from the first time they lead a class. There are particular teaching metaphors that they will find especially helpful (or not), there are particular techniques that they will be more or less comfortable teaching. There will be a personal balance between silent demonstrations, demonstrations with step-by-step explanations, and helping individuals one-on-one.
Style of aikido is a little trickier. On the one hand, I think a dojo that expects a 5'4" 125 pound woman to have technique that looks exactly like a 6'4" 250 pound man's is probably not a place where I would encourage anyone to train. On the other hand, if both people are teaching at the same dojo I would expect them to both have similar explanations for *why* their technique works, and similar reasoning behind whatever body-type driven adjustments they make. (I suspect this is part of what Tarik meant by "principle-based" instruction.) If the chief instructor argues that aikido is 90% atemi, I would expect junior instructors to be able to show where the atemi targets are in any particular technique. Conversely, if the chief instructor rarely demonstrates atemi, I wouldn't expect junior instructors to emphasize it, either.
It also depends on the relative ranks involved. The more senior the chief instructor is, and the more junior the junior instructor, the more closely I would expect the junior instructor to follow the "company line."