The Hopper 3 will not play 4K from YouTube as it does not support the VP9 protocol that YouTube uses for 4K. (VP9 came out after the Chipset for the Hopper 3 was designed)
I'm streaming Defiance in 4K right now and unlike the other day this is streaming at 90Mbps average. The other day Dish was only able to do about 3Mbps.