Soft and hard decorations follow cloth.  They're not rigid or soft body dynamics.  Hard decorated groups over multiple polygons of cloth can actually bend to follow the cloth.  They don't move around their own center or some such.  They just follow the cloth underneath them.

I don't have a grip on exactly what you're trying to accomplish (I could use the references myself), but I can tell you what I do when I want something to sim a single rigid body, like a pendant on a necklace: I create a one poly dynamic piece that goes underneath it with an invisible material (0 diff, 0 spec, 1 trans, no trans falloff).   The limitation is this doesn't work for other things colliding with it, because that one poly doesn't actually have thickness.

Also, you might want to make this a figure with dynamic and rigid parts.   IIRC, bopperthijs has a free beach chair in Freestuff that shows how that can be done.  Yep, he does.

If you have the money to upgrade to P10, then the answer is rigid body dynamics.