the engines are totally different. the transfer ports are hideously small on the clone motors. the cluctch housing is cast onto the crank housing. the dome area is shaped quite differently as well.
as far as you 2bolt/4bolt scenario, its only partially correct.
with a Quality motor like a Zenoah, the 2 bolt versions are very high quality. only the 4 bolt zenoahs are less likely to blow a cylinder gasket. other than that, the 4 bolts zens are not any less or more durable than the 2 bolt zens.
its not the number of cylinder bolts, but the quality of the materials and build. which is why the Zenoah brand motors are the top dog. the are made from high quality materials with well paid labor that take pride in their work.