I'm going to assume you are referring to the differential ratio and not the trans, 2020 rear diff is available with 5:38's I'm not aware of any 5 speed gear ratio changes for the 2020 transmission. The 5:38 diff would be preferred for low speed crawling and will take better advantage of available torque especially at very low speeds My primary use is some 55 mph and under blacktop to get out to Arizona desert and unimproved fire and remote access roads so the 3:7's work great.
I am turning 2000rpm at 60mph. Is a nice cruise
My math says with the 538 hearing that would be 41 at 2000. I think really they just want us to stay under 45 and hyping it as a rock crawler