I have now made the flatbreads with potato flour instead of potato starch. The ones with starch are denser, if that makes sense, although they taste the same. The texture was more bread-like with potato flour. I haven't made crackers yet, but I'm wondering if the crackers would be better with potato starch, while the flatbread is better with potato flour.
I will have to make a batch of crackers, half with potato starch, half with potato flour, and compare!