The most "drapey" quilt I ever made had a batting of Mountain Mist Blue Ribbon 100% cotton. Every time it is washed, it gets softer. I saw the quilt many years later, after multi machine washings, and it was like one of those wonderful old-timey quilts that cost a fortune -- soft in color and soft in texture. The only thing about this batting is that I would not recommend hand quilting it as I did! Afterwards I found out that it had oils and seed bits in it that made hand quilting more difficult than it should be. If I wanted to hand quilt and achieve a similar texture, I would turn to Quilter's Dream 100% cotton batting. It gets good reviews for hand quilting ease and shoudl shrink and soften the same as mine did.
One of the things to be careful about with 100% cotton batting is to quilt closely enough.
I made a similar quilt out of poly batting at the same time. Also saw that quilt many years later. Alas, it had not held up to the machine beatings and was a lumpy mess. The child who owned it still loved it, though!
I haven't used Warm n Natural in quite a few years. Its advantage is that quilting lines on it can be far apart; the needlepunched scrim holds it together well. The reason I don't use it is because I find the drape to be quite stiff compared to 100% cotton.
Mary