I use a down quilt not a bag but I just shove it into my pack and let it take up any empty space. I find this to be easier and more comfortable than trying to deal with stuff sacks, I do the same thing with my clothing. I do use a pack liner to keep everything dry of course.
I have used lighterpack for years and it still seems to be the standard in the ultralight "scene" but I am finding myself switching to pack wizard. For one thing, I like that I can easily copy gear lists I see on it vs. trying to manage a bunch of bookmarks of lighterpack links.
I figured, it's about time for me to post instead of just lurking! I have somewhat of a background in ultralight backpacking or at least thinking about it since my 2015 PCT thru attempt and am just starting to pursue getting into hunting with the plan being to start with my first turkey season...