Orange points are auto generated by the engine and therefore considered by NPCs as the least reliable.
If there are blue and red path points both in the direction the NPCs AI is sending it, it will always choose the blue ones. It's like telling them "this is the easiest way to navigate through this space", handy if you don't want them to get distracted in a large or cluttered area that's pathed. To setup up an ambush you should create an AI package for your NPC that either has them wait there, or has them patrol a route that includes the balcony (if you only want the possibility).
Pathing just tells them how to get from here to there, where they wait and weather they wait around or go somewhere is all controlled by their AI packages. The AI is usualy setup on schedules (patrol this route from 8:00 - 5:00, eat supper from 5:00 - 7:00, sleep from 9:00 - 6:00, etc.) which makes the NPC behaivour more realistic, but you don't absolutely have to. For example you could setup your ambush PC to wait on the balcony 24/7 if you didn't want to bother setting up multiple NPCs with shifts, it's all up to the level of detail you want to put in.
WT