It would be the petite, making the 5" HS. You would be cutting 5" squares, and the strips would be 1 3/4" & 2 1/4". Based on a layer cake being 5".
Personally, I'd use fabric not precut since it would need cutting anyway and to me that equals waste. Then, I'd do the 6" HS. cutting 6" [or 5 1/2"] squares, and strips of the same size as above.