Here's what I used. I'm not sure of the exact thickness, but it is pretty thick. Way beefier than what was on the 4R, which lasted ~ 10 years.
https://www.amazon.com/dp/B07X9XNV3K?tag=ihco-20
Our 2021 has the same thing, although not quite as advanced. I knew to look for it because I noticed the same on our 2010 4R earlier this year. On the 4R, Toyota had installed a thin film between the trim and the paint, which eventually wore through and allowed the trim to crack the paint...
We have a Black Widow AMC 600-2 Aluminum. Easily carries a 450 and a 125 with no bags. Very little sag.
Wobble is solved completely with this Anti Rattle Hitch Pin & Shim.