The new M&PS, especially the competition ones, do benefit from the Apex stuff but it's by a much smaller margin than the 1.0s and the early 2.0s. I'd not buy Apex replacement parts for the those models unless I was competing at the highest level. That money is better spent on ammo and mags.
Get an SBR if you're talking home defense. Very simple and easy to do now.
Look for a lightly used 75 if you elect to go that route. There's a shit ton of them out there for great prices. Also the P-10 works very well too.
Thread tax: here's pics of the target that I was referring to earlier when I mentioned my Bodyguard 2.0 possibly keyholing rounds. I think you all are correct about hanging paper and subsonic rounds.
HP ammo
View attachment 9714511
Ball ammo
View attachment 9714513