As to question one: I would press the seams open. But I would also make a small test block using scrap fabrics and the batting and backing you intend to use. This way you can see ow your machine will handle the layers but also how to adjust the decorative stitches will work.
Question two: since I’ve never made a potato chip quilt in this manner, I have no input.
Question three: unless I am misunderstanding how you plan to construct your top, I don’t see a way to accomplish QAYG method. You will simply be quilting the entire quilt which as you wrote entails having a lot of bulk under your machine throat.