styling webform into 2 columns
What I did for one of my client in order to get the webform in two columbns, was to create two "Fieldset", containing the fields for column 1 and column 2.

Then with css, I added to my webform this property :

.webform-component-fieldset {width:50%; float:left;}

Of course, there are other ways of doing it, like display:inline-block, and maybe you need to be more precise with the css so you don't mess up other webforms.

And if you don't want the title of the fieldsets, you can do a simple:

.webform-component-fieldset legend {display:none;}

I think that's the easiest way of doing it.