presentation sketch is pretty much what it says. a sketch which you would present.
A quality which would be fitting to show a pro spective client.buy the book design sketching it breaks down the different types of sketching and the sort of levels required. For your case i would suggest a gorgeous 3\4 view showing of your product in its best light and then other supporting views of exaplnation. Look at Yo’s concept 14 shoe on his website or even the marker and verithen pencil tutorial on here
The only wrong answer here is something that is not compelling.
I’ve seen awesome presentation sketches done all in black marker on newsprint that are more compelling and communicative than the full color 20 hour renderings that sat next to them on the wall. I think it is all about communicating your idea. A line drawing might do that best, or a full blown pastel rendering might do that best. Take a look a Syd Mead’s Portfolio 1-3 books. The line drawings are as compelling as the gauche renderings.