I have an Apex trigger kit in my M&P 2.0. Awesome. Really hard to believe the improvement (over stock) till you try it.
I have a couple FNS strikers in FNS slides and will buy a couple more for the other slides fairly soon.
When I had a question about the function of the new Apex strikers in my two slides I PM'd Apex off the FN Forum on a Saturday evening and got a response within a couple hours. We PM'd back and for a couple times and then I was given an e-mail address for further communications. Only one was needed as I think I got it figured out and fixed to my satisfaction. The trigger reset on the factory strikers was darn near as good as the Apex M&P trigger kit. When the Apex strikers went in the trigger reset to striker release distance increased noticeably. A little stoning of the sear to striker contact area with 280 and then 600 grit stones took care of it completely on one striker and very nearly completely on the other (continued dry firing made a quick improvement on that one).
That's my experience with Apex.
But, back to the CZ issue/question. The CGW parts are just excellent. Never any issues with the stuff I've bought. So I can't remember ever needing to contact them. I talked to either CGW or CZ Custom on the phone once (can't remember after 3 years or so which one) with questions about a slide release and got the info I needed. I never ordered a hammer from CZ Custom since I was ordering the adjustable sear from CGW I just ordered the hammers from them, too.
I figure anyone ordering from any of the three vendors will be happy with what they order, or if not a quick phone call will get things straightened out.
Visit the Apex web site. For the M&P and FN pistols/parts they have lots of tear down, parts replacement, and put it all back together videos.