immersive npc at night

[Lionheart]

is there any mod to force npc walk with torches or use spells at night and make them see worse?

[Stormsong]

Most NPCs with a torch in their inventory will use it when "appropriate."

As for putting detection more on light level and less on sneak, look up Realistic AI Detection (RAID) on the SE nexus and realize there are multiple settings. So if one feels off you've got some wiggle room.