Just hooked up a 2019 Shield Pro alongside my Apple TV 4K. Got the Shield mostly for the Plex and also because Apple's blacks were raised in Dolby Vision content.
The only quirk I wasn't expecting (because I thought everything was pretty much standard nowadays). . . the Shield is putting out a slightly brighter picture than the Apple TV. In SD content, my LG OLED65C8 requires a brightness of 53 when watching the Apple TV to not crush blacks and bring out shadow detail (while preserving true black). Yet the Shield requires only 51.
Since my Sony 4K Blu-ray always matched exactly with the Apple TV, I was expecting the Shield to be the same. I've settled on the middle-ground of 52 since they're all using the same input on the TV (via receiver). I guess if I want them to have their own brightness, it'll be back to using the separate inputs on the TV. =(