I find when I’m sewing that it does matter which needle on which side is on top side or bottom. Left under right tends to give me a pretty wave like your picture, right under left gives me a curve and a hump over it. Kind of two semi circles. Side by side is too hard to explain, but one way is very sloppy and the other way is straight, but boring, and often uneven in length.
oh, I should say, I use Glover’s needles, often don’t make a line, and don’t use a pony. I often feel lucky if I don’t bleed as much. Lol.
Your kids stuff is great!