Just a couple of thoughts.

Perfect down - containing only plumules and no quills - will recover from severe (huge and unimaginable)compression. Try it if you have any left from a project. But compression will push quills through the shell of bags and garments. It also can crimp quills - which can cause lower loft down (450 to 550) to lose loft because it relies on the quills.

Framelesss packs hold shape better if insulating garments (including bag) are stuffed free to fill space. If the insulation is toward the front of the pack it will hold denser items such as food closer to the back.