There are many vBulletin forums out there. The thing is the community and it being relatively easy to modify means you can look at two vB boards and get almost entirely different experiences.
Default vBulletin can be found on Jelsoft's site:
www.vbulletin.com/forum
Somewhat customized official site for modifications:
www.vbulletin.org
Both of those are using fixed width by default. We will have both fluid and fixed, including conversions of some current 2+2 styles.