We owned a 1st Generation Xterra with the 3.3l V6. It had a towing capacity of 5,000 lbs. It had a Class 3 Hitch. I added a tranny cooler and setup the 7 pin wiring and brake controller. We also had a 6,000lb Equal-i-zer Weight Distribution Hitch with 4 point sway control. We towed an almost 5,000 lb Rockwood Roo 233. It was a Hybrid Travel Trailer with 3 fold down beds. With the beds closed, the trailer was about 19 feet long.
The Xterra towed very well on flat land. We towed from PA to GA and GA to TX with it and the Xterra did very well. Your 2015 Xterra has a much larger engine 4.0l V6 with 265 HP vs the 170 HP on our 3.3l V6. You should have no issues towing on flat land. Head west and you might have some issues climbing mountains. We towed into some of the small mountains of Eastern PA and the Xterra did well, but it was no speed demon. I would just get behind the big rigs and slowly climb up.
You should be able to tow all three of the campers you listed without a problem. Most weight distribution hitches allow you to carry a little more weight on the tongue. Our Equal-i-zer hitch bumped our tongue weight capacity to 600 lbs.
-Michael