When talking about the body part (not, for example, entrances/exits), what is the difference between these two words. Based on looking at these two pages (for 口 and 口元) I'm guessing that the difference is that 口元 deals with the outside part of your mouth, i.e. the lips, the shape of the mouth etc, while 口 deals with the "whole package" so to speak (the inside of the mouth, the tongue, the words/language one uses).
Am I right on this? Can these two ever be used interchangeably? Are there other parts of the body that work (grammatically) the same way? (I tried 鼻元, but I got "root of the nose", which doesn't make sense to me...)