In my experience, dry firing can improve both the DA and SA of any C75 variant in tuned or stock configuration. Even my pro package CZs tuned by CGW have seen some improvement from live fire and dry fire. There is no replacement for break in that i have found.
I think that 2morechains makes a valid point above. Especially for the DA, changing the hammer and Trigger Return Spring can have a significant impact on the weight and the perceived smoothness of the DA pull.