I too have suffered with input lag in rage 2.
I was going to refund it but I will give the deadzone setting a tweak and see if it helps
Let me know if you have solved with this settings. I use mouse and keyboard and the input lag is present
This was an issue at launch with Rage 2, on most platforms. It was so bad that they had to finally add a deadzone slider to the game which was not there at launch, so it isnt just you or Stadia, the aiming was so bad it was near unplayable.