You don't have to run the emulators on your NAS. In fact, you probably shouldn't since your NAS is unlikely to be plugged in to any video output.
Pretty much anything can just point at your NAS's shares for access to any and all emulation. Heck, I think an Amazon Fire Stick can even do it.
If your buddies want to bring over Shield Pros to play, all you should need to do is let them on to your WiFi and have read access to your roms or ISOs directory.
So... I guess I'm not quite sure where you're going with the question?