I am saying that you can do just the TQ arm and most likely see a drastic difference in smooth traction on and off road. The TQ arm will benefit any type of driving and suspension set up. The Gen2 has a lot of torque and so the axle twists mostly because of the stock soft suspension. I personally did not like the feeling of the rear end even at cruising speeds, there was a back and forth sensation almost like engine surging. It was exaggerated on un even slab concrete. Although it is not a dramatic feeling its a personal thing that most will only notice now that I have brought it up.
I did not run the TQ arm with stock springs but I feel it would really help with that back and forth sensation. Its not going to fix the side to side jittery rear end but may help that a little bit with that, the springs make a huge difference with the side to side motion there by settling down the rear.
In stock form on the street in the rain you can get axle hop under light acceleration so I would not say its a mod only for those who are pushing the truck. My truck sees about 75% street use and I see the benefit of the TQ arm in normal driving stock springs or not. Lots of people never change a thing on these trucks and love it.
As for warranty issues they would have to prove that the TQ arm caused whatever issue that came up. If warranty is a concern then don't touch anything and run bone stock.
Eibachs in front and Icons or Deavers in the back make the truck feel firmer more like that European car feel and the TQ arm takes away that axle hop making the truck more to my liking while driving normal or sporty on and off road.