Well, the Rubi you posted is heavily modified, what is your budget? A 2015 will probably run around $35,000, and then add another 15-20,000 in modifications (to make it like the one you linked). Depending on your level of experience, and willingness to bang up the body, it would be capable for any trail in that level of build.
If you are just doing back roads and forest access roads, you don't need to go to that extreme. Mine is on 35's, with lockers and a little trail armor (not to be confused with bullet armor!!!) and can do 95% of the trails we have, more if you're willing to risk body damage (which I am not willing to do yet).
Cross country trips....the Wrangler line is not the most comfortable to drive for long periods, but that being said we have driven ours to Nashville and back, which is around 5000 Km round trip. Fuel mileage is not the greatest, ours gets around 15L/100KM the way it sits today.
Stay away from fullsize if you plan to run any trails, they are just too big. But if you are staying on forest access roads, full size is fine and over you a lot or cargo capacity. When we do our 3 day "overland" trip, carying 2 adults, 2 dogs, and all of our camping gear, we are packed to the roof in the Rubi, but we also don't pack lightly.
If you have an specific questions about the Rubi, let me know.