Some old school advice here, some good, some bad.
As for the transmission advice about shifting, keeping it out of OD - Wrongo! The 6 speed in the F150 is designed to tow in all gears, all you have to do is hit the tow / haul button and let it decide. It wil not hunt for gears like older / other transmissions, it will progressively "lock out" the taller gears after a couple failed upshifts.
On hills, the truck will fairly aggressively downshift and use engine braking to keep the speed in check. It will quiet often downshift to a gear that will keep you at the same speed going downhill, even after you take your foot off the brake.
Lastly, if you don't already have, get the OEM brake controller, it's way better than even the best aftermarket controller, and it integrates with the truck to manage any sway.
Enjoy your truck, it is up to the task, and a wel match combo IMO.