SIngle axle trailers do not have near the tire issues as tandems or triples, so IMO the brand of tire is not as important. That said, trailer tires for some reason dont seem t o last more than about 5 years before they become time bombs.
DO not get P rated tires and good luck finding ST tires in a 13" wheel. I dont think they exist.
ST tires are what you want. Yes they are rated to 65mph only, however myself and thousands of others tow much faster for long distances without issue on ST tires. Don't worry about it. Drive as you normally would or feel comfortable with and dont worry about the tires (unless you're rollin at like 90mph or something.......). More importantly, make sure the bearings are well greased.