It's easiest for you to start HERE in the beginner's section of the Wiki if you haven't found it.

Width impact is almost entirely a matter of personal preference. Wider blades are easier for a beginner to strop as they are are easier to keep flat on the leather. Wider blades hold more lather between wiping it off. Narrower blades can be easier to maneuver. The most common size is the 5/8 and that's a good starting point.