The best personal earpro combination I've used is the Opscore AMP with the NFMI earplugs. I can hear everything but it's as much reduction as really good foamies under really good muffs.
Can I re-range without waiting 10 seconds for the range button to default back to "I want to range again" mode instead of "scrolling through info I don't care about" mode? IE, like the current Terrapin X
The only downside to the USP at this point is the cost and relative scarcity of getting the slides milled for a RMR/RCR/ACRO. The HK USP is still a workhorse.
Short config is 7 dB louder at SE vs. the long config.
A flat cap is not included or sold separate because it's a silencer part-- see the Magnus thread for discussion.
You wouldn't want to shoot it with a flat cap anyway, less than half the recoil reduction of either braked config.