I have a gas 07. Hauled many trailers. Gasser will get it done but best to keep the load under 10000 lbs, I really start to notice the weight when starting and stopping when you start getting close or over 10k.
Yes poor fuel economy and high RPMs are the down fall. My truck could have used a few extra gears in the transmission. At a 100km p/h it was in the low end of the gear, and not a lot of torque. It's sweet spot was between 120 +, then it would hold its speed better on the up hills.
Fuel was also a bit of a pain. My gas truck with the big trailers I needed to stop for fuel in every town about 200 km apart. It wasn't empty but would be below 1/2 tank and probably would not make it to the next town an hour and a half down the road. So lots of stops.
To sum it up, there is nothing like pulling with a diesel but the gasser will still get the job done.
I tried with one back in the day, got there but was a lot of stops and some serious screaming on hills. Tranny will be fine, they don't have enough power to hurt it.
Had a 07 quad cab short box with 3.73 gears, 6 spd manual. Pulls fine, stops fine, hard on fuel, 300-400 km on a tank to fuel when pulling. Yes on the screaming RPMs, as that is where it gets its max torque. Head winds will be a pain in the ass. When going to Vale or McBride, have to fuel in Whitecourt (top up), Hinton (top up) and then final destination. I have made it to Edson before with enough fuel. Usually drove at 110 km/h.