A horse trailer isn't the same as a camper, the load is more centered over the axles on a horse trailer than an RV. Same can be said for a flatbed or even an enclosed cargo trailer. You also have the added benefit of being able to move the weight around at least somewhat to get weight off the truck.
An RV basically has its weight distribution fixed, and you can't really move much of it around. Furniture, appliances, beds, etc. are all fixed in place. Sure you can move clothes and items you add around, but generally speaking it's not enough to offset the weights. An RV is also wider and taller than a horse trailer generally.
All that said, I have seen the effects of pulling without the proper equipment. It is disastrous. It's not safe.
I almost watched my FIL make the same mistake. He was picking up and moving a 38 foot travel trailer with his F250 to take 50 miles up to their vacation property. Tried to convince him to buy at minimum a WDH, because it had something like 1200 lbs of tongue weight. He didn't, then tried to get on the expressway. He couldn't run over 35 mph, and even a small side wind almost shoved him off the road. We ended up getting off the expressway and going to find one. I had to set it up in a parking lot for him so he could get it up there. He got a cheap one and didn't get a sway control, so while it was better...it was still all over the place.
I'll say it again. Bare minimum you're going to want a WDH, even if it's a basic one. Sway control is highly suggested, even if it's a stand-alone one which for some reason no one on this site but me prefers. With that much weight trailer brakes are highly suggested, so if you don't have a brake controller get one. I doubt you'd need air bags, but even then those are something to add in AFTER all of the above.