Third, magazine safety or not? What are the pros and cons of this?
Mag safeties are good for…what are they good for again?
You can "turn off" the gun by dropping the mag. Some LE agencies like this because a LEO can disable the gun if he/she is about to lose it in a wrestling match with a suspect. Some civilians like this because the gun can be left at bedside or in a car glove compartment with less concern that an unauthorized user can fire it.
Manual safeties will do this, but you're a lot more likely to notice that the mag is out than when the little safety lever is off.
One other con is that some practical shooting competitions require that the pistol be cleared and decocked before a shooter leaves the firing line. With a mag disconnect and no manual decocker, it is impossible to safely drop the striker unless the shooter carries a spare empty mag for this purpose.
I regard mag disconnects as a matter of personal choice.
All that being said, in states where they're not required, it seems that dealers very rarely stock mag-disconnect M&Ps. The ONLY mag-disconnect M&P I have ever
seen was a used one at a pawn shop; the clerk told me that the former owner was a sheriff's deputy who had purchased the pistol through the department's LE purchase program, and he could only order one that met the department's specs.