Definitely try to press away as much as possible. I know that once you get a quilt layered and quilted, and then if you wash it up after it'd done you definitely don't notice any seems peeking through. I make a lot of quilts with white (bella solids more than kona) and haven't had any issues with those solids. I don't know about the white on white prints, I just never like the feel of them because it feels more like a screen print tshirt than typical print fabrics, and I don't like that.