I can't speak for the difference between the 6000# and the 7000# axles, but I know for a fact that the outside bearing on a 5200# axle is smaller than the one on a 7000# axle. All three of them use the same spindles and brakes. Maybe the 6000# axle has the larger outside bearing, but we wanted the larger outside bearing and the 8 lug wheels which meant we needed the 7000# hubs. They work great!
ST rated trailer tires have a 65 mph limit. I didn't know that until this year.
