If you're talking about the physical piece that goes in to your ear, the only impact they have with sound is how well they seal your ear to the outside world. It helps passively cancel out some ambient noise.
Naturally, most high-end IEM's like your x10's are built around their particular acoutic setup that is given by their shape. The folks who build it have to account for that heavily, because technically the shape should influence the sound, but with such a heavy pricetag you must trust that whoever built your earbuds accounted for that aspect of delivery in sound. So, in general the influence of earbud shape on sound quality is negligible to naught. They will, however, influence your comfort while using them, and it will most definitely contribute to the passive noice isolation.
That being said, in my experience, I've noticed that IEM's as a whole can tend to sound a bit more muffled than other headsets, like over-ears. This does not mean that individual IEM's sound is influenced by their different shape. High end IEM's should sound as natural as any pair, including over-ears, simply due to their driver being built precisely to work in its specific acoustic enviroment. Lower end IEM's will sound more muffled, but it is due moreso to the poor quality of the driver than the actual bud.