Steam can already stream to other Steam installs in the house. I have personally only found it to be playable with turn based games.
I just received mine yesterday.
I noticed no lag when playing injustice gods among us.
did you have it wired or using wireless?
how string is your host PC & video card?
I did not try to run an emulator though as i don't have any installed on my main PC.
Will try mame this week though.