A PShape object is just a datatype for storing shapes (SVG or OBJ) and PeasyCam :
provides a dead-simple mouse-driven camera for Processing
(from the repo)
So those are not related to what you described earlier with your picture, you need to use a PGraphics object in order to draw on a separate buffer isolated from the rest of your sketch.
You only need to use your instance of PGraphics in order to display what you want. You can still use global methods in order to load your OBJ file. (like you did in the code above)
The above code looks correct so you are good to go! 
(remember that to format your code on the forum, you can use the </> button instead of the quote one)