The smell is only noticeable when walking behind the car while it's running, nothing to worry about IMO but some are annoyed by it.
I don't know what your guy is talking about concerning the "weird" fitment on a 2013. My 2013 STi fitment is exactly, and I mean exactly, the same as my 2011 WRX was. In fact I'm still using the same downpipe - Invidia Catless. And I just swapped the turbo to a 20G XT-R, and fitment is exactly the same on that too, FWIW.