A trailer size and construction type is a consideration best resolved AFTER you have a firm idea of your cargo. Cargo that can be loaded evenly and is modular, such that the tongue weight can be "tailored", permits the user to use a "tight" trailer close to the cube dimensions of the cargo.
However, when you are throwing a CC TM into the mix, the complication is multiplied. In an enclosed trailer, the TM must first be placed within specified zones that permit cooling air access and egress, while also sharing a space with large, heavy accessories such as a loaded hose reel(s), fresh water tank, etc. All of this while balancing the load for the aforementioned acceptable tongue weight. Dual axles give a measure of latitude, inasmuch as weight distribution is a tad less sensitive to the resultant balance.
I've seen a number of trailer installs that were less than ideal, because too small a trailer was used, leading to either poor cooling placement to get balance, or poor balance to achieve adequate air flow. Strategically placed vents, doors, fans can certainly help some of the cases. And for some, this is the route users take. Cooler climates can also help.
When I was ever in a position to make a recommendation, I advised the buyer to put together his anticipated cargo (TM, etc), then lay it out and deduce the size and style of the trailer that would be required.
Again, the OP does not specify what is being transported. If it is removable modular support "stuff", certainly a tight trailer fit can usually be accommodated. Especially where access aisles and/or other open space zones are also not required.
