This plugin can probably be configured to generate any form you can possibly imagine, but the result is a long (long, long, long) page of settings that each have to be configured separately.
(Srsly, the administrative interface of this thing is a nightmare. I mean, I understand how it happens: you start with a nice, clean, simple interface, and over time and the addition of many, many features, it turns into spaghetti. The plugin is apparently undergoing a major overhaul. Hopefully the interface will get a workover in the process.)
And yet? Out of that endless array of options? There is no single checkbox or button for disabling the plugin's default stylings completely and allowing you to style the form via your own style sheet. The plugin itself does not use a stylesheet. It uses *inline CSS* (??? so bad!!!), with the reasoning that this way the stylesheet doesn't get overwritten with every update. Okay, here's how you overcome that: let me use my own stylesheet. *One* setting to give the location of that stylesheet. Or even no setting -- there are lots of plugins that will check for a standard CSS stylesheet name in the current theme directory before defaulting to its own stylesheet. Gigpress comes to mind.
If you want to use your own stylesheet, you have to define your own classes in the form setup for every. single. element. of every. form. OMG.