Make sure you select type as "Mobile" when you first add a recommendation widget.
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.
Play around with the "Count" and "Per Row" settings to your liking, as well as further Customize the style in the "Customize" tab.
This is what it would look like on preview (note that the test store images are different sizes hence why it looks not aligned):
Note: We have a new System Config section called "Email Config" that has only 1 option for "Mobile widget output width (px)" which is set to 375px (industry standard). We can override this per client if needed. If your subscription plan doesn't include system config, contact us at [email protected] for updating this value.