3. Stealth weapons are stealth only when you takedown NPC before they fire. If you hit them but they did not die fast, they will shoot their loud weapon and draw more guards.
This right here is why the best weapons for missions (where you
don't intend to just go in guns blazing, like a tipped-off settlement massacre) are ones with very high single-shot damage. Even if they're not silenced, the only one that's made
immediately aware of your location is the one you shoot, so as long as you can take them out in that first shot, you're good.
You could run a covert mission with an unmodded L-6 if you really wanted to. Just make sure to change position the instant you pull the trigger and make sure nobody sees you - it usually takes a moment for them to go from their "what was that" moment where they freeze up on hearing the sound, to actually turning around to look.
(that freeze is one of the trickiest parts of using audio masking on an executioner - if you
don't silence it, the sound of the shot makes them stop in their tracks for a moment which makes them much easier to hit!)