I'm a believer in the Apex parts. In particular the Striker block.
The USB which comes with the D/CAEK fundamentally reduces the initial take up profile and removes the grit that eventually gets polished off the OEM part by firing.
The Sear trips at (IIRC) 5.5 lbs, vs. stock 8 lbs (again, if I recall right) so the press is much easier to manage.
The Apex parts addressed what most consider one of the major problems with the M&P FS9 Gen 1, the trigger (the other being accuracy).
I liked mine a lot, but I liked it much more with the Apex kit. If money was an issue I'd just get the USB, you'll notice right away.
I bought a set of Tipton snap caps in 2015. I don't use them much. I think I tried a few mixed in some magazines, but I could not self diagnose my problem to say they helped.
Regular dry practice can help a lot more.
Good for trying to find an instructor. It really is probably the quickest way to diagnose things you are doing wrong. If I was made of money I'd have done that earlier myself, but I'm retired and have lots of time and like to figure things out for myself.