I vote for no sashings. The one with sashing, all I see is polka dots! The other fabrics show up better in picture 1 and also it interacts with the neighboring blocks so well without sashings.
No 1. No sashing, makes me dizzy.
No 2. Row sashing, Reminds me of an old graveled country road.
No 3. Around the blocks sashing, Looks finished. Like this one.