Concur on the lockup differences. A Glock can be detail stripped effortlessly and quickly.
DIY can make a huge difference on a Glock trigger and action. That I know for sure, without compromising function/safety. Sig trig? Don’t have one:-(
There’s a pretty good market for Glock armorers.
I know of two that set up shop in gun stores and at gun shows and do nothing but “fluff and buff” and part replacement.
The day I picked up my Glock 22, I had the 5.5# disconnector replaced with a 3.5# unit. Very nice for accuracy. I’d probably stick with 5.5 for a CCW gun, but I’m currently carrying my P229.