Recently we got to do some research on trailer hitches and horse trailers

[HooptieWagon]

13. No real experience with 5th wheel here,

but I've done a hell of a lot of trailering with bumper hitches, towing boats, cars, and cargo. Here are some thoughts:
#1 cause of trailer accidents is over-loading or improper loading. Be mindful of the weight you are loading in the trailer, and its placement. The tongue weight of the trailer should be a minimum of 10% of the total weight of trailer and cargo...less than that results in swaying, which is dangerous, as it can result in loss of control or blown trailer tires from overheating.
Generally, vehicles today are smaller than the past. While a small trailer without brakes can be safely towed behind a full-sized truck or SUV, care must be taken to ensure braking capacity isn't exceeded. If no trailer brakes, then trailer and cargo weight should be added to the towing vehicle's weight...IOW, don't load a half-ton pickup with 1000lbs, then hook on a 1000 lb trailer without brakes, that will exceed the braking capacity of the tow vehicle.
I have found trailer surge brakes work better than electric brakes when travelling forward, especially on the highway. However, surge brakes are a real pain when backing up, especially uphill. Might want to try both types before deciding which to get. All trailer-braking systems have a safety brake in case the trailer comes loose, as far as I know. Some are also equipped with parking brakes.
Trailers tow better the closer the hitch is to the rear axle of the tow vehicle, which is the big advantage of 5th wheels. Extended-length vehicles usually add that extra length behind the axle, making how they handle when towing by a bumper hitch worse. A load-levelling hitch is a big help in those cases.
Trailers tend to be neglected until they're used. Tires go bad from UV exposure, lights stop working due to corrosion, etc. It is a good plan for regular maintenence, like an annual inspection, even if the trailer has low miles during the year. Replacing the tires every couple years is a good idea if you are loading the trailer near its maximum....they get flat-spotted from sitting, and
are weakened by UV .
Manuvering a double axle trailer around tight corners is harder than a single axle trailer. But don't overload a single axle trailer. Get the double axle if a single axle is marginal for the weight youre carrying.
I'll edit to add more if I think of extra tips.