Picking up objects of different heights

Preface: I’m completely new to this, my first maker “thing”, so please forgive my ignorance. That said…

If the airpicker is used, and I have three cubes of differing heights, how do I make it pick up each one without having to set the z point for the top of the objects? Is this even possible?

Does it detect the resistance of the object (Is that what ‘StallGuard’ is?) and know it has contact?

I’m afraid of breaking my dexarm by having objects of different heights and it trying to move the air picker down beyond it’s height. If I have a 15mm, 30mm, and 50mm box for it to pick up, would that have to be pre-programmed for each object’s location?