With the exception of the 'inventors' of any religion, everyone who practices the belief systems of said religion is doing so based upon the teachings- whether they're written or verbal seems irrelevant to me. If written is the crux of the question, then anyone practicing after their respective sacred texts were written would be those described in my original statement.
Thank you Kukovian and Denuseri (and Racogzy for excellent questions!) for an insightful look into your customs. I'm sure I'll come up with a question or two if that's alright.