Both had very smooth performance without artifacting and GRID tended to go up to between 80 and 100 Mbps, greater than GTA which was smooth until it hit the 95 mbps mark at which point it produced a spike.

Image above is captured at different points in different games, mainly to show input latency, Case 1 is GTA 5 and Case 2 is Grid 2. So for my case this means full 1080p 60 FPS video with decent input latency but its still a little worse.

I've noticed that steam link likes to crash on the device in situations where its 'not being used' so if you switched to another app or something, expect to have to close and restart the app but once you have started streaming it can sustain good quality for your entire session. The Ematic 4K Ultra HD is actually rather nice and can do steam link at speeds of up to 80-100 Mbit/s,giving me a good image and the rest of the device seems pretty nice but it is my first android tv box so any comparison is futile beyond stating that it is fast and good enough but the last security patch was done in 2019, leading me to suspect it won't be further updated which is unfortunate. I have been testing the device I mentioned and here are my thoughts on it:

Steam link device 4k