Since with the heavy options I’m looking at I’d be more limited by payload/younger weight, right? So would it be better to just stick with the 3.21? Seeing people with 10-12 mpg is scaring me a bit ha.
I have the Level 1 Laramie 4x4 with 3.92. I drive conservatively and average from 15.5 to 16.5 MPG in mixed city/highway (to and from work). On a 200 mile road trip that I took, I got 17.8 to 18.5 MPG running at 77 MPH. Running at 70 MPH on the highway I averaged 19.6 MPG. I live in Florida where there are no hills; so my averages may be higher than some. However, I think these people reporting 10-12 MPG have a lead foot or don't maintain a constant speed. I am completely satisfied with the mileage I get. For me, 3.92 and Limited Slip were deal breakers because I bought a truck for work and performance; not for gas mileage.
Since I'm writing, I'll give you my two cents on some other options:
1. 8.4" vs 12". I have the 8.4" no NAV and I like it. I don't miss NAV because I have a phone and a Garmin. Personally, I have no need for the 12" UConnect.
2. Level 1 vs Level 2. I have Level 1 and it is fine. The only thing that I don't get with Level 1 (that I would want) is the 360 degree camera. I don't care about lane assist or forward collision; I know how to drive.
3. Off Road Group. Initially I wanted it; but in the end it didn't matter. I will put the MOPAR 2" Lift and some bigger tires on my truck when the factory tires wear out. Skid Plates are cheap and easy to do yourself; so they really shouldn't be a decision maker for you. Lifts look cool; but I can do this myself later. Plus if you are truly worried about gas mileage; a lift and big tires are a sure way to kill it.
4. Towing. If you get the tow package; you will probably regret it unless you like the giant RAM towing mirrors. Skip the Tow package and just order Trailer Brake Control.
5. Rear Wheelhouse Liners. I have these. There isn't much to them but they make the truck look better. I like them.
6. Floor Mats. I have the MOPAR front and rear rubber floor mats; this was a must for me and they are quite nice and functional (keeps things clean).
7. Fuel Tank. I have the standard tank and get around 400 miles out of a fill up. The 33 may be convenient at times; but not really necessary for me.
8. RAM Box. Nope, not me. Really, I just don't like the look or the fact that they lower your payload and your usable bed space. I'll get the MOPAR sliding tool box for $500 if I need it; then at least I can take it out when I don't want to use it.
9. Under Seat Storage. I don't have it; I like the flat floor with my seats folded up (I think you lose that with under seat storage). There are two smaller bins (that are standard) by the rear doors to stow things like tie down straps, gloves, etc....they work for me.
10. Axle. I know I said it before; but yes, get the 3.92. Its a truck. I think you gain more with the 3.92 than you lose; the gas mileage isn't that different.
11. Something you didn't mention. I didn't see you mention E-Locker or Limited Slip. There is a lot of debate about which is best. We can leave that to another thread; but get one or the other. Without them, you can expect to spin tires from a stop or around corners when the roads are wet. I have limited slip and have no worries about spinning tires when I pull out.
12. I think you mentioned a 2018 or 2019 RAM earlier. After having a 2018 as a loaner I can tell you that the 2019 is a HUGE improvement. Go with a 2019 New RAM (not 2019 Classic).