I use my steam deck docked primarily to stream from my main PC to my living room. I haven’t noticed any battery degradation when I do use it in handheld. I got it March 2022.

Also if you happen to be using Emby as a media server, the emby theater app image supports controller :)

Retrodeck in your case then if you just want a simple setup.

I use mine docked fairly frequently. No major issues that I’ve had. Just note that if you change the games resolution to higher than the steam decks native screen, you’ll sacrifice framerate for it.