Welcome to the forum.
Generally speaking, the heaviest handgun will help keep it from moving while aiming an pulling the trigger - weight resists movement to an extent. This weight also absorbs recoil to help from developing a flinch in a new shooter, for instance. I think the lighter guns for carry are great. No good to keep a gun that is too heavy off your body in case you need it. With practice, light, short barreled guns can be shot fairly accurately as well. Don't get all bent up that a SD gun should be able to hit a tennis ball at a 100 yards. A bad guy attacking is likely going to be close up -- enough so that you might not even have to aim!
That said, there are a bunch of the factors leading to accuracy, type of gun, sight radius, sights themselves. I went through a number of different types of handguns before discovering the holy grail of accuracy in 9mm (for me) and that is the CZ75 design. The C100 is a clone and reports are good so. . .
Now if you are looking for a range gun, then consider getting an even heavier all steel design. If your intent is to also carry it the C100 or PCR or P01 (aluminum frame, CZ designs) MIGHT be great shooters AND carry guns!
It sounds like you are going down the right track -- attempt to try a bunch of different weapons to see what suits your body (and perhaps get some training so you don't reinforce bad shooting habits).