Hi Ashman,

As you want to be save with batteries, than look ad the discharge rate of the battery. Higher is better.
The motor will pull from the battery his energy and as the discharge rate is to low, than the battery can die and in some cases depending on what battery you use, start burning.
Look what the discharge rate is and what the esc can handle.
Personally I prefer a 36v or 48v setup.
Your motor pulls less amps to get get the same result.
Those higher voltage motors have also a bit more power.

Personally I would go for a higher voltage as you need to pull a lot of weight.
Those high voltage motors have more power to do so and pull less on the battery.
You go further with less ah on a high voltage setup, than on a low voltage setup.
And check the discharge rate of the battery. On a high voltage setup, you don't need the highest numbers but look for quality. Cheap batteries will die a lit sooner.

I was looking to ad a one wheel with a motor on it as a trailer. But I changed my mind for now.
Than I need to charge it every night and as that is not possible, than I only pull extra weight.
But I decided to upgrade my trike in the future to electric with a rear wheel motor and higher than 250w.
Here are so many bikes, that the government change the law on bike lights and other rules. They couldn't check them all. I know people that removed the speed limiter and added a thumb stick to power the bike without padeling. The motors are so silent, that it's hard to see if he gets suport from the motor. In some cases you must look good to see if it is an electric bike.
That is why I probably use a 250w motor in the future, without speedlimiter and ad a gas handle, so I don't have to pedal constantly.