What is the difference between 9sp and 10/11sp cranks/chainrings?
8, 9, 10 and 11 speed chains are progressively narrower to accommodate the necessary closer spacing of sprockets in the cassette. The distance between the inner plates is the same, but the width of the outer plates and rivets is different.
The main difference between crank sets designed for 8, 9, 10 and 11 speed chains is the chainring spacing as you have guessed.