Single axle trailer, probably will weigh something like 4K loaded. Load Range D should do fine. (It likely came with Load Range C, but it's very likely they would be running close to their weight rating. That's not something you want to do with trailer tires.) In terms of weight - go to a scale after loading up for a trip and get your true loaded weight. Sometimes using GVWR is ridiculous. I used to have a 21 foot trailer with 3,500 lb CCC - fully loaded weight was 2,700 lbs below GVWR.
IME, any brand tire works fine if you always drive below their speed rating (many are only rated for 65 mph) and don't overload them. I've always run cheap tires and the only tire failures I've experienced were due to damage from road hazards. (Lost one to a screw, and another to a larger piece of metal. In both cases the culprit was still in the tire, so it was obvious what caused the failure.)
I currently use Kenda LR D, 15" tires on my trailer - a Korean brand, made in China. 35K miles so far on this set with no issues.