Welcome to the forum from Virginia. Do you hear this when going over bumps or potholes? Go ahead and Jack up that side and wiggle left right and up down on the tires and have a look underneath. Try a pry bar to move the steering and suspension parts around. Hopefully it shows itself easily.
Welcome to the forum from Virginia. A few questions. Did you hear this going up/down hill or both? On flat areas? Use tow/haul mode? Any noise when not towing? Did engine temp get high? Any DTC lights? Any brake issues?
I switched my GMT 900 to Arnott a while back and could kick myself in the stones if it were possible. Others may chime in with better results. My factory shocks lasted 13 years so why I decided to go cheap is beyond me.
Joseph returned his to stock so he’s a good source. If you don’t have any service suspension lights there’s probably a bypass resistor installed. It’ll connect to the factory wiring on top of your strut tower. Same for the rears.
Start with the ground connections. Even if they look good peel back some of the coating and look for corrosion. Cleaning the ground areas is good for them anyway. Once done check your battery and alternator. Usually comes back to the simple things.
Yes AWD is all the time. No high or low thus your mileage will suffer. Do you need 4WD? Denali generally has most every option available including leather which may or may not be good for your dogs. Not all Denali came with a 6.0 but most did. I believe the suspension on the Denali is different...