I tow a 28' (32' overall length) trailer that is 6700lbs dry with a 2018 Silverado LT 5.3 Crew Cab, 6-speed without any kind of factory tow package. I wish I had the lower rear end gear the max-tow package trucks come with. I never tow more than ~5 gallons of water in it. It's alot to tow, but keeping it around 65-68mph and a proper WDH + AirLift 5000 it's fine. I've towed it ~750 miles each way to the beach twice, once through the mountains in TN/NC. The mountains were nerve racking, but it handled it OK.
The only concern I've had with my setup is transmission temps when its hot outside in stop and go traffic. They can get up to ~220ish. I'm going to look into adding an auxillary trans temp cooler.