I am in the process of making a quilt using an oversized D9P pattern and I want the quilt to be puffy when done - actually more comforter like thank quilt like because the recipient likes puffy quilts.

When you make a puffy quilt, what brand/type of batting do you like best?

When my daughter asked for that on her wedding quilt,- I got some 'hi-loft' polyester batting - I didn't like it - but she was happy

Hi loft polyester batting. Very durable and warm.

Charisma uses Hobbs poly Down batting. she quilts quite heavily, but with less quilting i think your quilt would be puffy.

there are a number of high=loft batts to choose from- read the packaging and choose the one that (fits) your quilting plan (as in some need to be quilted every 2-4"-others do not need so much quilting)
if you do not follow the recommended quilting distance-if you use a batt that needs to be quilted every 2" and you quilt every 6" the batting will over time separate- bunch up and cause hard balls of batting in the areas between quilting lines-
you can however buy a batt that can be quilted every 10" and quilt it as closely as you want-
for high loft you do not want to densly quilt= it will flatten it.