HI Marv
Not to say I have all the answers so I will tell you my last twenty years of towing. First i just sold my 2008 Airstream 25 (5600 lbs dry and 960 in hitch weight), my wife and
I put 65,000 miles on it towing with a 2014 Silverado 1500 with a 5.3 and 6 speed trans. The truck had a max tow PKG and a 373 axle . The mpg around home 19/20, towing if i stayed in the 65/70 range was 11to 12 mpg . The last trip in TX and AZ running 75 to 80+ milage was 10 to 11. I never use cruise unless it flat with no wind. With all that said I am waiting for my Elite 2 in June and my new 2022 chevy 1500 with the 3.0 and 10 speed. For the last 20 years at work I have towed boat all over Michigan and other parts of the country. I have used GMC 1500 ,2500,and 3500 both gas diesel, tow from 5000 lbs to 19,000 lbs. When I grab a truck to tow I always when i could a truck that was rated for twice trailer as the load i was moving. By doing that it was a lot nice drive, and it also gave me the best tow milage. On the 5.3 i had it ran down the highway towing @ 2200 to 2450 rpm in 5 gear and would up shift in to 6 on fall roads or with a tail wind. The Oliver weights less then my own boat by 1000 lbs a nd the hitch will be about the same. i tow the boat all over MI with out a weight equalizing hitch ,but with Sumo Springs installed. Boats do not tow near as good as Airstreams or Olivers. So with all that said I have a 2022 chevy 1500 with a 3.0 max 4 wheel drive with a 10 speed . 12900 lbs tow rating and a 2100 lbs payload I my add Sumo Spring ( 1000 lbs units) mostly to stop the bounce when towing the boat , they create a lot more bounce than travel trailers. The GM 6.6 gasser are testing a 10 speed for 2023 to help them get some milage ( family works for GM trans) lots of power for heavy loads around town but I wouldn't buy one for la daily drive or long hauling.
Jim