You can now specify the layout you want to have for mobile under the Layout section of the email widget editor.
Our suggested layout is to have 4 items count with 4 columns in desktop and 2 columns in mobile.
To make the mobile layout possible, we have to breakdown the desktop row to multiple mobile rows. This is the only work around for the HTML responsive limitation for email.
Make sure to choose the number of columns for Desktop first and then see the options you can have for Mobile after.