Visual Composer Website Builder has a feature called Design Options where you will be able to control your margins, padding, border, and radius.
By making use of this feature you will be able to add specific margin/ padding on the specific device only.
For example, you want to give your button a top margin of 50px but for mobile-only, you just need to select the device type to custom, then select mobile.
When you give a top margin of 50px on mobile, it will not be affecting your desktop or tablet design.
This feature is so powerful that you can have your preferred design on your specific devices. You can watch this video to understand more about margins, paddings, borders, and radius.