We tow our 2600RB with a 2022 Duramax Tahoe using a 12,000 pound Equalizer and it's solid. There is a little twitch occasionally, but I have been in Midwest crosswinds and had an abrupt hard brake (make sure you tune the trailer brakes properly) at highway speed during an atmospheric river to let a pickup slide by on its roof as it shot from the fast lane to the slow lane shoulder, and never any more than that little twitch. And two blowouts at 70 MPH 100 miles apart in South Dakota were a big nothing. 11-12 MPG
Now GM reliability... Can't recommend. Gassers have lifter issues and diesels have oil leaks/consumption issues and the 10 speed with the diesel in particular has a really bad valve body fault they just launched a recall on. If you are buying a used one that new, chances are it has a fault of some sort. Ours had some misrouted harness issues and the dash gave me a grocery list of faults, but amazingly didn't kill us or leave us stranded. Ours got denied lemon law status, even though it was out of service for more than 30 days in 30 months. To be honest, I think we're past the worst of it, but glad we got the extended GM warranty.
We have the RST and i figured for sure I'd be getting smaller wheels, but I like the 22 inchers just fine. Handles stupid well without the trailer. Unfortunately, if you don't get the air suspension, the camber under load is criminal. The idiots didn't design the IRS on a tow vehicle to stay in camber. You add 0.1 degrees of negative camber per 100 pounds of weight on the rear axle, and it starts at -0.5. I got to 30k before a dealer performing a tire rotation noticed belts showing on the inside edge. And I told every dealer I went to we were towing a TT cross country... I had my alignment shop set it up as close to neutral as possible and probably need to flip them on the rims every 15k. There is one aftermarket solution and that is King air shocks, because air bags won't work on IRS. But brakes show more than 80% remaining at 35k with a good 20k towing across the northern part of the country and up and down the west coast.