Plugin Form Design

I need to create a form for the wordpress plugin. This plugin will be used on several websites. My doubt is how I can make the form design as general as possible so that it fits well and blends well with the design of the wordpress theme. Since the form can be placed on the page, in the column or in the widget area.

I also need to keep in mind that most WordPress themes are now “responsive” to reflect the growing browsing of websites on mobile devices.

I would like to know your opinion on this topic.

Thanks at Advance.