First of all, pretty much all the trailer tires available are cheaply made junk. There just isn't a big market for them, so the major manufacturers don't put any R&D money into developing quality offerings.
Second of all air pressures. Running at max is a very bad idea. You are far more susceptible to punctures as the tire is like an over inflated balloon, and we all want to avoid dealing with flats when we should be fishing. Being over inflated also reduces the tire's contact patch, negatively affecting traction while cornering or braking, and actually leading to a faster wear rate on the tread itself. As for fuel consumption's relation to psi, yes there is a lower rolling resistance at higher pressures, however a very large increase in air pressure (say of 40 %) will only lead to approximately a 2% reduction in fuel consumption. The rolling resistance is more a factor of casing/tread design than air pressure.
What you need to do is run at the correct pressure for the load the tires area carrying - not grossly over inflated, or under inflated. Provide the tire dealer with a good guess on loaded weight and ask them to look up the recommended psi.
And yes, radials are what you want.