The difference between travel trailer, toybox, and cargo trailer is generally that travel trailers do not have the fold-down rear door or a "garage" type storage area. Toyboxes are a version of a cargo trailer that still has the drop down rear door that also acts as a ramp to load toys (motorcycles, atvs, buggies, side by sides, etc) but typically has a semi-finished living area with fold down bunks, some type of kitchen, bathroom, and holding tanks (fresh and gray at the least, black tank too if there is a restroom that isn't cassette/composting toilet). Cargo trailers are just covered enclosed unfinished trailers and may or may not have the drop-down rear door (sometimes there are barn-door style rear doors, sometimes removable ramps, but generally there are always large rear doors to enable loading of larger items).
In my experience the insulation in all of the above is generally quite low quality and inefficient, but then maybe just most of the people I know buy budget trailers that skimped on the insulation.
The 5th wheel and giant toy-haulers are a class of their own and are more akin to a house on wheels with an integrated 1-car garage than to a typical recreational vehicle. They also require a pretty hefty tow-vehicle as they frequently come in over 10,000 lbs when loaded.
