The late model Dodge Quad Cab doors swing open forward like a normal crew cab. Early model Dodge Quad Cabs had suicide doors. I think the change happened somewhere around 2000.
The longbed makes more sense for carrying a truck camper, especially any truck camper longer than 8 feet, cause the axle is further back, having less weight behind the axle and more weight distributed to the front axle.
On most trucks, an extended cab short bed is about the same length as a long bed regular cab and an extended cab long bed is about the same length as a crew cab short bed. The best compromise for hauling a truck camper is the extended cab long bed, if you're worried about wheelbase length.
If you're getting along fine now with a regular cab, then obviously you don't really need a crew cab, you're probly just looking for some more interior storage space and occasional passenger room. The extended cab fits that scenario very well without making the truck unecessarily long while still keeping the full 8 feet of bed length for carrying a wider variety of campers and/or a longer camper. The long bed also allows carrying an 8 to 9 foot camper and towing without an aftermarket heavy duty hitch and extension bar that are needed to carry 8 to 9 foot campers with a short bed.