You CAN tow more than the rating. But it's harder on the vehicle. You should look for a trailer that will be at least 1000# under your tow rating unloaded. Remember, the tow rating DOES NOT include weight of passengers and equipment. You lose 400# with two average adults, you may be more or less than that. Add a couple kids and that's about 600#, then throw in weekend luggage and you're up to 1000# -- and you haven't even included extra stuff like chairs and such in the camper. Add another 500#. So now you're 500# over the recommended tow capacity-- but I'd call that good assuming trailer brakes and load leveling hitch. If you're boondocking and filling water tank... 10 gallons is 83#, so that's another 354# for me (43 gallons) -- many newer campers hold 50+ (over 415#). Plus the weight of a generator and extra supplies -- so you better go 1500# under capacity. I tow a 7200# camper with a 8400# rated 2003 Expy (tow package), but I don't boondock. I wouldn't tow anything bigger, and would prefer a 25-26' -- but my wife liked this camper, so...
You will need a brake controller to run safely without overloading the vehicle brakes, though in theory it should be ok. You just have to anticipate stops and drive a lot more carefully without those brakes. And a load leveling hitch. Unless you're an experienced tower I wouldn't tow anything near the capacity without trailer brakes, a load leveling hitch, and a sway control on the hitch. Without those I'd say a max of 1/2 - 2/3 the tow capacity, and even then you have to be more careful and not just motor along.