I already had cheaper HD Netflix subscription, and didn't notice difference between it and UHD Prime/Apple TV/Hulu. I only noticed that I didn't have UHD when I was cancelling it, to be honest. Maybe my TV is not big enough or I am too far from the screen for this to be noticeable (65" Sony OLED TV about 3 to 4 meters from my coouch).
Regarding the pirated content - I just started, so my experience have pretty low sample size. Still, majority of shows I downloaded so far are in 4K. The only one in 1080p is older show, for which I think there's no 4K source material.