They built two full suits for the main Predator in Predator 2. One sculpt to fit the 7' tall Kevin Peter Hall, and another full sculpt for the "normal sized" stunt guys. The stunt suit molds were also used to create all the Predators on the ship at the end of the movie (again, for normal sized guys) except for the Elder suit (also played by Kevin Peter Hall), in which they used the hero suit molds from Predator 1, with Predator 2 hands and feet and a modified Predator 1 mask.
Yes, the did make stunt and hero Predator 2 helmets and yes some of the details are different.