I'm sure its the latter (except for the fact that Kanami'll inevitable face her shadow self and get a Persona by the end of it)
I always kinda thought they were the same thing, as in there is no difference between Persona 3 and 4 regular shadows and the shadow selves of the characters. The way I see it the Shadow world is a direct reflection of humanity's psyche, every shadow that the investigation team fought "belonged" to someone from the real world. The only reason that the investigation team's shadows were able to mimic their host's appearance was that the presence of the host in the shadow world strengthened them to a point were they were much more powerful than the other shadows around them. Does that make sense, or am I completely off?