As a general rule, wheel bearings will run cooler and last longer on trailers with taller tires.
With 8" wheels, those tires are turning high rpm at highway speeds. On a lightly loaded small trailer, it's probably not going to be a problem. Unless you like to run 75 mph for sustained periods, lol.
You may have read that on a Uhaul trailer, and it's 45. In reality a few weeks ago I made a 520 mile trip, (and then I came back) most of which at 70-80 mph highway speeds. Don't try it with those little wheels. I don't think that there are any actual laws regarding towing speeds, but states are allowed to make their own laws. If you want to upgrade, check your clearances, measure the bolt pattern, and see what yoju can find to fit.
I made these up for my trailer.I used them along with the ATK bike shoes.With hindsight I found that the ATK bike shoes were overkill along with using my bike clamps.They do offer peace of mind that I will never lose my bikes but I could have done just as well with a bike chock and saved some money.One thing to be sure to do when mounting the D-rings is mount them a little forward of the footpegs so the clamps pull the bike into the chocks.If you are real brave just weld up a steel box to put under the frame and tighten the clamps down.Reinforce the D-rings under the trailer
and the heftier the better.
You have no need for tie downs once it's all tightened down with the turnbuckles....and yes I just turn the bar you see in the picture to tighten them.