So I received many emails about the last piece. Here is more on the discussion.
An NPE pistol MUST be DA, or have a heavy trigger, because an NPE pistol will be carried without a holster. NPE, by the way, stands for NON-PERMISSIVE ENVIRONMENT. I would never carry a striker fired pistol that way for reasons mentioned. Specifically, the deeper the concealment...in pocket...in jock strap...without something protecting that short light trigger, you will in fact at some point, touch the trigger while accessing. And if the "touch" is during a time of duress, you will shoot yourself. It is not a training issue...it is a life and circumstance issue. Do it if you wish, but you will one day remember what I wrote here.
Thus a Glock 42, 43, Shield and any SIG based on the 320 trigger - including the P365, is a Social Compromise Pistol and NOT an Non Permissive Environment Pistol. I will clarify the three basic carry categories below.
They are based on the environment you will carry in and the legal/social/physical repercussions if discovered.
Standard Combat Carry - Carried in a holster under light concealment. No serious repercussions if discovered. Permission is either granted specifically (license, badge, etc.), or generally as in "constitutional carry" (Arizona for example). While any weapon, including smaller versions can be carried here, these are the larger end carry weapons possible in this category of carry. In short...anything is legal here. Examples of what we see chosen for this situation.
Sig P320, P226
Social Compromise Carry - It is against the established rules to carry any weapon. These are still carried in a holster, but choice is made to decrease size to allow for deeper concealment due to socially established norms where discovery would be inconvenient. If discovered you may be asked to leave or dismissed from employment. Weapon may be carried holster-less but with some compromises in weapon choices (DA may be carried holster-less, but a striker fired weapon may not be). Examples below -
Glock 26, 42, 43
Sig Compact series 320, and now 365
S&W Shield series
Non-Permissive Environment Carry - Discovery means summary execution or immediate arrest with likely imprisonment. Few Americans actually ever carry like this, but some do. Some of us that have carried in the sort of places described in our President's recent comments, without the umbrella of an OGA or the US Gov, have carried in a non-permissive environment.
Holsters are proscribed. That means you carry without a holster or standard carry accessories. The reason is that there are times in a true NPE where you will wish to divorce from the weapon and not have tell-tale items indicating you were armed. Holster-less carry indicates either empty chamber carry for weapons like Glocks and M&P, or the use of DAO or DA/SA weapons like a SIG P239 or a revolver. Deep concealment requires the use of smaller weapons.
S&W J-Frame Series
SIG P239, and 230
I will say this (and if it offends anyone, please reconsider your chosen carry method as you will eventually have a mishap with your pistol) - Only a fool carries a striker fired pistol, fully chambered, without a holster.