Screens Stack | Optimum image size?

I have recently purchased Joe Workman’s “Screens” and
I would like to know in pixel dimensions what would be the;

・optimum banner size for background use (full image)?
・optimum image size on a Screens slide full image?

having issues with the image being cut off or bleeding into the
next “Screen slide” or “Screens page”

I also have the the Responsive Layout stacks and I’m not sure if I
should be using them with the Screens theme
I am using it with the Foundation theme (as suggested on the website).

Thanks in advance for any help