I'm not sure what you mean about quilting with rickrack.. I've used it in quilts (and prefer to have the ends encased in seams but not for the quilting. I would certainly boil any vintage trim you might find but feel pretty good about modern stock.
In my fish quilt I used the jumbo, didn't need to worry about color bleed. I sewed down both sides with a straight stitch.
I've used 1/2" white (poly) twice on two very different quilts in making fans what I call the Eleanor Burns Method. Halfway through is the 1/4" seam line, and it is already on the bias and helps turn the curves nicely. One was "Aunt Debbie Bleeds Blue" a sports quilt for an older lady, and the other was my Thanksiving themed top.