You are probably getting warmer. Hard to say from the newest video, it is a good one but there is just so much road and wind noise its hard to pick out the sound even compared to the in-cab videos. And of course with a gopro there is not really any directional sense to the sound and something is vibrating the whole chassis so just hard to say for sure.
Something in the drivetrain is vibrating, that seems pretty well confirmed.
Something is either out of balance somewhere or worn or damaged.
One thing I didn't think of before, if you go on a decently long enough drive of 20 minutes or better and stop it would be good to immediately hop out and try to fee the temp on the hubs, middle of the rims, and (carefully) the edge of the brake rotors. I don't think your issue is a dragging/stuck brake caliper but should rule it out. If one of your brake's isn't fully releasing it
could cause vibration and that hub/rim/rotor would be noticeably hotter than the others. You probably would have already noticed it by now though, it would probably smell when you stop the car and if it goes on long enough that rim will start to get discolored from the extra brake dust. It would stand out pretty well. Still one thing thats in the vague realm of possibility.
In terms of narrowing down the drivetrain noise, thats going to be tricky. There is a simple cheap device called a
mechanic's stethoscope that works really well for hunting down things like a noisy idler pulley or a failing power steering pump, etc. The problem is its tricky and dangerous to use on a drivetrain... if you could put the vehicle up on a car lift and safely run the vehicle in drive would be one thing. Not sure what to say there.
A little play in the carrier bearing doesn't always mean its shot, thats another tough thing. Like others said its far too early for anything in the drivetrain to be so worn that its vibrating but the unknown would be that possibility of an accident having tweaked or damaged something. Terrible things happen when a spinning drivetrain assembly comes to a sudden, violent stop.
I had a pickup truck that got stuck in the rear passenger tire while driving. The impact to the rim bent the axle, so that was replaced, but after replacing that I still had a vibration. Pretty sure I tried a new carrier bearing, and still had vibration. Finally I took the entire driveshaft assembly to a local specialty shop where they mounted and spin-tested the whole assembly, and they found that one of the sections of driveshaft was slightly bent. They cut and welded new driveshaft tube on, and spin-balanced the assembly and gave it back to me. I put that back in my truck with the new section of driveshaft and the vibration went away. The assumption was the twisting momentum that was going while I was driving forwards and then the sudden strike of the crash caused it to bind and tweak the driveshaft tube. I will say, when that crash occurred the driveshaft broke loose and was hanging so it was definitely believable.
Your pinion bearing at the rear differential where the driveshaft inputs the power to the rear wheels could be damaged too as another possibility. The setup on a pinion is kinda delicate and a very common source of vibration after a ring and pinion replacement. If some prior accident had caused a tooth to be broken off in there and replaced... I have a Pontiac Firebird out back (rear wheel drive car) and many years ago I had the ring and pinion swapped by a mom-and-pop transmission shop (changed the gear ratio for more acceleration) and they didn't get the pinion set quite perfectly so its had a vibration just like the one from your first video ever since. Pretty sure mine is a fair bit quieter but the same type of noise that wanes in and out rhythmically at speed.
For a vehicle this new with that kinda mileage pretty much for sure is the result of some kind of accident the car experienced before you owned it. Its almost unheard of for any drivetrain parts to go bad at the low of mileage. Not sure what your prospects of getting it covered under your powertrain warranty are. Its definitely a powertrain/drivetrain problem but if it was caused by an accident... I don't know. I think that is what I would try though, is seeing if you can get it looked at under warranty. Free to ask anyways.
Barring that you are going to need someone with a proper car lift so the vehicle can be ran safely with all wheels off the ground and use something like the stethoscope to pinpoint it, which is a dangerous multi-person job even for a proper repair shop. Alternatively if you could hunt down and borrow something like this you could probably narrow it down:
Amazon.com: 8MILELAKE Electronic Stethoscope Kit Find Engine Noise Diagnosis Scope Mechanics Tool: Industrial & Scientific
www.amazon.com