Up until "Dragonstone" (Game of Thrones, S07E01) we have only seen faceless men change faces, but when Arya takes on the 'Face' of Walder Frey she assumes more than just his face. She takes on his voice, mannerisms, stature, and posture. Certainly, some of that can be mimicry (changing one's voice, etc), but when Arya (as Walder) stands to make a toast she is like him in more than just 'face', we get an especially good view of the hands and his height.
So, how* does the 'magic' of the House of Black & White/The Many Faced Gods work in respect to this? Does putting on the face of another grant one more than just a face?
Note: other questions bring into question how or whether Arya still has access to that magic. For the purpose of this question let us assume that she does.
*Edit: By "how" what I mean is 'to what extent' or 'how far does it go'. (not by what 'magically principal' (ie is it a transmutation or a glamour). The reference that points out that memories even come with it. The names "The Faceless Men" and "The Many-faced God" focus our attention on the 'facial' aspect but the 'magic' really appears to cover allow the 'wearer' access to the identity, in both mind and body.