I have a 2017 Rebel with the 32 gallon tank. I absolutely love how it drives. I've driven it from Minnesota to California, Key West Florida, Alabama and up to Alberta and British Columbia on various trips. It rides beautifully and gets 18-19mpg overall. I can push 600 miles on one tank if I get a tailwind
If you're looking for extra practical storage get the Rambox. I love the out of the way secure storage. It makes the bed area a bit smaller (but more rectangular). If you use the bed for hauling alot then maybe skip the Rambox but if you don't use it too often the Rambox is so handy. I haul things on occasion and the bed size is just fine. My Rambox has all kinds of things in it...towels, tools, Windex and other cleaning supplies, windshield cover (sun blocking cover for inside), tow rope, etc.
I have the air suspension and really like it. Its never had any issues, even in the cold up here in Minnesota during the winters.
Good luck on your choice! Love my Ram!