Oh gotcha, I just run standard 2k monitors with steam link to a (2016?) Nvidia sheild TV and never had issues. That's a fair point though, I think you can potentially get around that by changing the in-game resolution but then you would have to change it back when you're at your desktop so makes sense. Sorry I couldn't be more help here!

Probably not a super helpful comment, but when was the last time you tried steam link, especially over Ethernet? Now I'm not playing any competitive, rhythm games or twitch shooters or anything but I've had 0 latency complaints. Either that or could give moonlight a shot for just two options that are free if you want to give them a shot.