The pluggin is easy to use and will satisfy you if you accept all fields to be as long as your page is wide.
If you want to change anything in the css, you're lost.
Just imagine that: to add some personal css change, author ask you to create your personal plugin !
Don't think you can modify classes, most are impossible to find uout in the several css files.
If you add a class to the ninja_forms_display.css, nothing happens using it.
3 hours lost trying to find out how to change field lenght. I resign.
Good plug in easy to work with, if you don't expect a good display.