Scenario: It's night, and a man is walking home. He sees ahead there is a woman going in the opposite direction as him. Knowing not to stop or approach her, but his presence makes her nervous. What would help further in this scenario if anything?
I think there is a cultural thing around nods. I would definitely not recommend, in this situation, doing a nod that does not feel natural to you, so either do whatever nod you can actually pull off casually, or skip the nod.
There is also a locale specificity... Where I live, people don't usually nod or otherwise acknowledge strangers on the street. Some places you might be expected to smile and nod or even say hi.