M&P 9c trigger weight

I'm considering putting an aftermarket trigger in my M&P 9c. I have absolutely no experience in aftermarket triggers, but I hear lots of people talking about Apex triggers. I'm not really sure whether their triggers are drop-in, for the most part, or whether I'd need a gunsmith to put it in. When people say they "put an Apex trigger in" to their M&P, what do they mean? The action enhancement kit? The sear upgrade? The flat-facing trigger? Any of the above?On a related note, how light of a trigger is too light for a carry gun? Their competition trigger is 3.5 lbs and their duty trigger is 5 lbs. I'm not all that certain why a trigger would be safe for competition but not for carry, to be honest. The gun isn't going to be firing unless I pull the trigger and I'm not in the habit of fingering my trigger just to mess around. Is there something I'm missing here? via /r/CCW http://ift.tt/2uNL3op