Towing capacity without a WDH is 6000 pounds (not 6600) with no more than 600 pounds on the ball. HD Tow ups that to 9200/920 but only with a WDH. Shouldn't need one for this trailer. The brake controller is part of the HD Towing Option so you're good to go if you need it.
Assuming your bass boat and trailer weigh 3500 pounds they'll be be less that 350 pounds on the ball. You and the truck "won't even know it's there."
Read the owner's manual on setting up electric over hydraulic brakes (if your trailer has brakes at all).
-- Chuck
PS You might want to delete your two other identical posts -- multiple posts just fragment your responses.