I’ve heard of SNOT (studs not on top), but this is full-on “studs not on the outside”.

The pieces along the corner of the dark red and white building don’t look like Lego to me. If they were part 4070, there should be a seam visible on the topmost piece where the part is recessed. I’d like to find out how the designer made it if it is legit, but the behind the scenes pics on their Instagram are not accessible without an account. Their Flickr is also inactive and I’m not seeing any results via image search.

Edit: came across this offbrand piece today that very well could be what the designer used

Wonderful!

Two questions: those dark brown minifig hip pieces along the top of the tallest building, how are they affixed? Also, those little grey 1x1 “cars” (eg one atop the closest building, what piece is that?