I use 7/8" DF satin ribbon to wrap the waistbands and have no problems with the tulle underneath peeking through even when it's stretched out. But then I usually have about 5 knots per inch so maybe that's why
I also tie the bow on upside-down, then double-knot it (tight!) so it doesn't come loose. I use 7/8" ribbon for the bow, although I have thought 1.5" ribbon might look better, I just don't have the funds to buy it lol. It doesn't have to look floppy - if you make the loops of the bow shorter, it will be less "floppy".