am I going to have problems fitting something this big in a lot of campsites?
If getting into every campsite you might ever want to camp in and every tight gas/diesel station, restaurants, etc. and being able to go off road without issues, get a truck cabover camper. With towing a trailer comes some trade-offs. The size and low height of a TT to the ground (compared to a a truck camper) is offset by having much more inside room and that comes at a cost of being able to maneuver the trailer into spots. If you are good at it the maneuverability is not that big an issue. If you are not good at backing a trailer into a tight spot, keep the smaller trailer. Everything is about trade-offs.