DRW or SRW with 19.5 rims and tires will provide the load capacity for a 3k lbs. boat and 4450 camper. You have roughly 350 + 4450 + 3000 (for the truck) for 7800 lbs. and the 19.5 wheels will each support 4400 for a total load capacity of 8800 lbs., and provide a 1000 lb margin.
The hitch strength needed depends on the weight of the boat and the length of the extension. A 48" extension is going to put 4x as much torque on the receiver as will a 12" extension. A 6000 lb. boat is going to apply double the force of a 3000 lb. boat. For a 3,000 lb. boat and trailer load and a 18" extension the Superhitch is overkill.
My factory hitch is rated for a tongue weight of up to 1500 lbs. and a tow load of up to 13,000 lbs. and a 3,000 lb. boat is well within its capabilities even with a modest extension.