Awhile ago I crewed for an SCCA C-Sports racer. I asked him what the best class was to get started and go racing. He replied "pick the class that feels like a race car to you", point being if you didn't like the car/class you'd eventually lose interest. I believe he was right. Same thing for boats.

On the dude boats - dude boats happen two ways - one is that the boat picked requires two dudes. The other is that two dudes want to go racing and need a boat that can float them. Non-dude boats typically have a crew weight that excludes dude crews. Having a mix of boats helps ensure wider participation.