Once the wall is up, it will slow down everybody. I'm assuming we will have security cameras with motion detectors along the entire border and also have a decent staffing of border agents.
So the second somebody enters the wall perimeter, even before they try scaling the wall, an alarm will have gone off and border agents will be rushing to the scene and will detain anybody that even tries (scaling the wall).
I assume this will be pretty much the game plan.
You are 100% correct. The wall is to delay and this allows the BP to respond and be there before illegals and drug smugglers scale or get too far.