Several friends of mine have them and seem very happy with them.  I do know you need a 2500/250 or higher truck and be sure you have the right length truck bed for the camper. 

You also want the special hook-up (hydraulic I think) for removing the camper from the truck otherwise it's really difficult to remove. 

We have one of those Sunlite pop-up campers for our 3/4 Chevy. It is a 8 foot and our truck has a 6' bed so it goes out over the tailgate. That wouldn't work pulling with a bumper pull. My husband has a little fishing boat and the tongue on the trailer is long so it works without jackknifing issues. You can buy an extension for your hitch and I have been told that works, but I would just buy a camper that fits in the box of your truck. It was easy to put on, just back in and line it up. They are nice and convenient. I contemplated this set-up too but went with a gooseneck living quarter trailer. You could probably pick up a  used camper somewhere pretty easy. The pop-up kind are nicer, less weight. You'll need a second person to help you hook up to your trailer though as you can't see a dang thing behind you when the camper is on.

Might be a better option than sleeping in your trailer!

I have had two different "pop-up" truck campers, both were lightweight  (FourWheel and Phoenix) smaller models. I have pulled trailers with them loaded on the truck, but not horse trailers only boat and utility trailers. 

I really like them for what they offer, but they do have limitations. First is that they are pretty small, unless you get a really big model.  If you do get a big model, you will need a real big truck to haul the camper and horses and be legal/safe.

In general they can be somewhat of a pain to load/unload depending on the camper. You need to be on pretty level ground, and typically it is a tight fit so you have to back the truck in very carefully. Mine have had manual (hand-crank) and hydraulic jacks which are simple and cheap. The problem is to unload you have to raise the trailer, then move the truck, and then lower to a more userfriendly stable position. This takes some time, as each corner has to be raised/lowered one at a time. If you really wanted to take it on and off frequently, the way to go would be electric jacks that all operate at the same time. This would save a bunch of time.

Most people, including myself, just leave the camper on the truck for the duration of the camping trip. If I was staying somewhere for a week or more, it may make sense to remove it, but for shorter trips I just remove the jacks (less wind resistance) and leave the camper in. In general in takes me 30-45 minutes to fully load and secure the camper, not terrible but certainly longer than disconnecting a trailer hitch.

When shopping for campers, be very weary of weights. The GVWR of your truck will need to handle the weight of the passengers, all your camping gear in the camper (like water), as well as the weight of the camper and the tongue weight of the trailer. Most moderate sized campers with horse trailers will push the limits of even an 2500 truck.

Good Luck,

             Flush

P.S. There is a company that make a "frame" that is electrically raises and lowers the camper and "hugs" the camper to your truck. It is probably expensive, but appears to significantly reduce the loading/unloading time. I'll see if I can find a link. Edit, I found the thing I was thinking of, its called "stablelift"  //www.stablelift.com

Stablelift is what my friends have on theirs.  They bought the camper used from fellow member in our trail riding club and we used it for several years and even trailered from South Fla to Montana several times.  He ended up selling it and got a LQ trailer. 

They used to pull a 2H but now pull a 3H Aluminum trailer with it to hold all their gear and 3 dogs that they bring with them. 

Not sure if you mean actually pulling a trailer with camper on top and then a bumper pull horsetrailer?

I've had a pickup camper and GN trailer and I'll never go back to a pickup camper.

I like not having the heavy weight on the truck which you do need to adjust your driving more so not to sway.  I didn't like driving on a windy day.  It's much easier to hitch since I'm hitching be myself.  I don't have to hear  the grumbling about putting the camper on and off. 

When I'm on vacation I love being able to unhitch my trailer so I can use my truck to check out the local area, go out to eat, etc.  I like having the extra room in the truck bed to haul hay etc.  A GN is easier for me to back and I can always park and setup by myself.  If I miss my turn traveling, it's easier to turn around because I can do a u-turn where with a bumper pull I couldn't do it.