They work very well in the coop as deep bedding. Poops dry quickly in them, even in a damp climate. They don't mat.
No need to crush them. It doesn't hurt to crush them.
The only downside I've noticed in four years of using them full time is they will mold if you pack them super, super tight into yard bags before they are dry enough. That happened the first year I did only the leaves because I didn't realize I wouldn't need as many as leaves as I thought I would then. I tried to store as many as I could - a few bags more than I could easily fit in the a available storage space.
The first year I used them at all, I mixed as many textures as I could: shavings, grass, stalks from the garden, the leaves, etc.. I like that a little better than all leaves but not enough to buy shavings or store the other kinds of materials.
I don't know if all kinds of leaves work as well as the mostly maple leaves I used.