You can use CSS to set different image size for different category listing menus, like explained on that thread:
www.hikashop.com/en/support/forum/4-how-...eight-and-width.html
But you can't have different image size for different categories on the same menu item.
Indeed, we changed the way the popup is handled for images so that it chooses automatically the best size possible based on the user resolution and the image size. That way, these two options are not necessary anymore. If if you want a different popup size, you could just upload an image with a different size.