Update on my end. Just drove around on a couple different freeways at speeds ranging from 60-80mph in San Diego. For me it depended on the freeways I drove on, up to 80mph smooth as glass and others a slight shake but nothing terrible (no free way was extremely smooth either). I tried taking a video focused on a water bottle to try and gauge the vibration at different speeds and different freeways, not sure if it communicates it as well as I wanted.
This probably is not a popular opinion here, but I see this as a none issue (to me), some of the shaking I experienced is something I can live with and does not catch my attention unless I'm looking out for it. I personally believe it is caused by certain road conditions and the fact that the back end is light with no payload or anything being towed. At the end of the day it is a truck, and this is expected to me, I'm actually very impressed with the how smooth it actually is. Now maybe some of you do truly have a very big issue where it is truly shaking more than normal based on the explanations I've read, maybe I was just lucky. Who knows? Defiantly seems some people have something off on their trucks, whatever it is, I just hope you guys get some answers.
I talked to a couple of my friends that both have 14' F-150's and asked them if they experience any shaking/vibration and they quickly responded 'yes' and even called out a freeway that I experience the slight shaking as well. so it's deifiently not just GM trucks. If anyone has questions on my experience let me know, happy to answer.