The NPCs I'd say go for it. The shadows are a bit more tricky just because they're dangerous, they can swallow you up, and touching them has the same result. The only way to deal with them is to scatter them with a weapon. Gunshots, swords, anything works. You scatter them and they'll leave for a bit, but they'll come back eventually. From personal experience, getting swarmed and swallowed by a lot at once isn't fun either so don't ever go against them alone.