Natural, there are no stupid questions... (well, honest questions)

The reason people fetch with an offset or a helical is to impart spin to the arrow; the more spin, the better the stabilization of the arrow -- especially with broadheads.

You will be able to fletch offset with your straight clamp (I'm assuming you bought a Bitzenburger of a Grayling?). I pretty much just adjust my clamp to get the most offset I can and still maintain contact with the vane or feather the complete length of the shaft. If you try to offset it too much, you'll see you'll begin to lose contact at the ends; you'll have to bring it back in line just a bit to get good adhesion the entire length. Hope that makes sense.

Helical fletching is great, but can be tricky when it comes to tuning issues, as it's easier to get rest contact with such a severe "twist" in your fletching. Most people have gone to using helical only with fallaways. I myself used to fletch straight offset, but picked up a helical clamp off e-bay for my Bitza couple months ago since I'll be shooting a fallaway this year. It might be advantageous if you like feathers to fletch with those when going helical; they're a lot more forgiving of incidental rest contact -- as well as with possible encounters with brush or twigs on the way to their target.

Hope that helps a bit.