Yep like others you will need a DRW (Dual Rear Wheel). Even towing week ends you are going to be over loaded and you will not like towing your trailer. Not even for short trips.
As for what LP5 and LML they are the RPO codes for GM engines. The first being the new 2017 engine and the new HP king of the truck world.
The other thing is being that you are going whole hog with a Denali these numbers people are using may will be for a less loaded truck! Go to a dealer and open the drivers door of a truck close to what you are getting and see what the door sticker say for payload and max trailer towing!
Don
