There are generally 3 different types of crown molding. 38, 45 and 52 degrees. The Kreg jig has a tool to allow you to check what your particular spring angle is, then you set the jig to that angle. It simply holds the molding at the correct angle as you cut. Without the jig the crown tends to move slightly while cutting. A slight discrepancy can become a big gap pretty quickly. You still turn the crown upside down to cut.
The hangers are new to me. I just discovered them, and since I'll be working alone, they'll make holding the crown in place so much easier!