Our house is still fairly intact in terms of layout. Not a lot of walls were removed (thankfully!) and for most part the details are largely intact (a few notable and regrettable things missing: the two original ice boxes, the built ins in the top floor dining room and the butler’s pantry next to the original kitchen in the garden level).
Incidentally, the garden level is the most altered. Originally it was the floor with the kitchen and dining room for the owner’s duplex. I can’t speak for the time between 1910 and 1930s, when the house was a 3-family rental, but I do know that the previous owner retained the garden/parlor duplex layout.