One of the most important features that a form builder can offer is the responsiveness of all its forms. That means that the forms are designed to display properly in a variety of mobile devices and adjust to different screen sizes automatically.
This will save you a lot of work so make sure your form builder plugin of choice offers a responsive design.
Also a little tip: Multi column forms look great on bigger screens but when it comes down to filling them out on a mobile device it can be a pain and difficult for your user to navigate. Thus, it can be wise to design a separate responsive contact form to limit the form abandonment rate.