It is shittty. I wish I could find my power cable for the actual Steam Link Device.

Tested this out the other day. pC hardwired to router and laptop literally 2 feet away. It was entirely unplayable.

I recently set up a Sunlight server to use with Moonlight on my Steam Deck and the quality and latency are better than Steam’s native streaming option. You might want to try that.

I never got it working well on wifi and ended up cutting a hole in my wall so I could run Ethernet between the rooms

Yes. It only worked well for me when at least one side (Link or PC) was wired. If both were wireless, it didn't work well.

Only over a 5ghz wireless network connection.

Mine actually works pretty flawlessly over 5ghz even a couple rooms over. It seems to have improved when I got a better router, which is this one

https://www.asus.com/us/networking-iot-servers/wifi-routers/asus-gaming-routers/rt-ax82u-gundam-edition/

Edit: just to mention, I am using the actual steam link device.

A few months ago I was having issues using Remote Play over WiFi to my Steam Deck.

These are the steps I took to troubleshoot the issue and overall I ended up with a much superior Steam Link experience as well.

My Steam Link is hard wired but my computer is wireless. I recommend trying to adjust some of the settings I listed in my Steam post.

Best of luck, and I'll happily answer any questions that I didn't address in my original post.