Try installing https://moonlight-stream.org/ on the Steam Link. Uses Nvidia’s GeForce Experience to stream from your PC; works a lot better in my experience.
Can concur. The hdmi cable to my living room broke, and I tried steam link on my shield but it was way too much input lag. With moonlight however I cannot tell the difference anymore, it honestly feels as direct as having it connected via hdmi. This is with direct pc - cat6 - router - cat6 - shield though.