Larger models require special waivers from the FAA, as well as larger fields and stronger launch equipment to fly. High power rockets are similar to model rockets in that they still have nose cones, body tubes, fins, motor mounts and recovery systems. Its just that all of these parts must be many times stronger and bigger then those in model rockets. Nose cones are often made of thick plastic or fiber-glass. Body tubes are made of thick cardboard, phenolic or fiber-glass.
Fins are usually model aircraft plywood, plastic or fiber-glass.
Often, the larger sizes and altitudes of high power rockets require more advanced recovery systems that include electronic timers or altimeters and separate ejection charges. Many systems will deploy a drouge chute to slow the rocket just enough to be safe, but keep it near the launch site, and then eject a larger chute at a lower altitude to allow the rocket to land softly. While many enjoy high power rockets just for the shear size and power, many others are in the hobby for the increased payload capacity that larger rockets allow. Probably the most popular payload is some type of camera, whether its still, movie or video. All have been and continue to be flown.