How do I modify the teaser products display page in Kickstart Commerce?
You'll want to look into Display Suite. Its a great module which allows you to not only create new view modes, but use special layouts for each view mode and content type. If you also have the Omega theme installed, Display Suite will give you some fluid, responsive layouts to choose from as well.

To be clear, Display Suite will create a layout within your page layout. It is specific to the view mode and that content type. I say this because styling might get muddy if you use it too much or inappropriately. That said, it's a great tool :)