Best to have all tires on the same axle be as much alike as is practical. Same size, for sure. Same tread pattern is desirable too, so having all the tires on the rear axle be the same manufacturer and model is the best choice.
There is no need to be the same as the front axle, though. Some coaches may even require a different size front & rear.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL