#1 - you can still see well enough, especially if you equip yourself with in-game objects designed to enhance visibility, and especially if you have not implemented the fakelight disabling tweak. And at any rate the Darker Nights mod allows you to choose any level of darkness you like, including levels that are only mildly tweaked from the game's weak vanilla light.
#2 - you can shoot just fine too, read #1. plus there's night vision and targeting weaponry available for use that just plain have no use in vanilla lighting scenarios anyway
#3 - in regards to the bolded - even just reading the mod pages would tell you that yes, the NPCs do in fact react to the lowered brightness level and can't see as well in the dark either. whether it's indoors or outdoors, the darker it is, the harder it is for them to see or sense you. so there's no 'immersion breaking' there.
http://www.nexusmods.com/fallout4/mods/676/?
Yes it is immersion breaking when they can magically see you but you can't see them.
He updated the mod, it wasn't always like that. That came outta nowhere. I already tried that mod awhile ago.
Still too dark with a decent reshade. Lights on PA helmets/pipboy only go so far (see a couple feet in front of you). Not straining my eyes.
I am enjoying my hella dark nights I have already due to a cinematic reshade I have -- that mod is overkill if I add it on top of that.
Opinions be opinions. So whatevs.