This isn't a projector or anything video related question really, it's a PC and PC software question.
In my experience, PowerPoint allows for a slide presentation to be played on monitor 2, and you can show whatever you would like on monitor 1. Any laptop with dual video outputs can be configured so that the connections to the two video outputs are setup for monitor 1 and monitor 2, then you set PowerPoint to play the presentation on monitor 2, and you put whatever you want on monitor 1.
You control what is plugged into monitor 1, by physically plugging something into your laptop.
Same with monitor 2.