I didn't do grouping test yet and I read that KWA are clone of KSC and KJW are clone of Marui. I had a home made mofidy hammer spring on my KJW and both are equal, both have strong kicks. I will chek for the mag catch and I'll answer back.
Also forgot to mention, for people experiences with this new version of the KWA M9, a list of compatible upgrades would be great:
high flow valve
enchanced recoil and hammer spring
6.01 thigh bore