First I will address the hives.
Because I run telescoping covers I cannot push 2 hives together, they are kept roughly 2" apart because of the covers. This space would fill with cold air and not really accomplish much. By placing the styrofoam in between them and taking up that space they then share a common side away from the cold and wind. I used to just wrap everything as singles but doing things this way I have 1 common side and cut my wrapping time and material almost in half. If I ever came across even more cheap/free styrofoam I would put a piece across the backside of the 2 hives before I wrapped thereby only having 2 sides open to the elements (I have already done this on 2 of my more exposed windy yards).
As far as my nucs go though, without the telescoping covers I just shove them together as best I can, and use styrofoam on the 2 outer sides of the entire bundle, but not on the 2 ends where the entrances are. A big piece of styrofoam covers the whole works and that's it. The nucs actually only have 1 side each (the front) exposed to the outside unprotected that way.