I think the first one is best. It looks quite realistic, whereas I think the other two would look very obvious as QR codes, even when the grass turns green. I'm not a big fan of grass QRs myself, since it's so hard to actually make the paths blend in. It always looks visually jarring to me. The first path is supposed to stand out from the ground and look like a different surface, which is why I think it looks the nicest.