I have a 35xx Plus, and the retroarch Ds cores were very slow, unplayable.
Im using muOs and switched to drastic Steward (external) and the games are playable now
if the sound is playing in windows, then enable desktop audio recording in obs, or try this http://smallbusiness.chron.com/hear-microphone-through-computer-speakers-56535.html
updating luma didn't solve it, he tried to download something from freeshop after updating and the download stopped like a minute after starting and the freeshop froze