The hum is a grounding issue, particularly if you can touch things and make it go away.
This is an extreme example (120 Hz in the US).http://kozco.com/tech/audacity/clips/OpenShieldHum.mp3
Are you plugging into the front of the computer? Is it any better if you plug in the back? The desperation method is a conductive wristband you wear during the show, so you're always touching the case. Do you have an old house? I've lived in three older houses so far and all of them have had at least one wall outlet wired wrong.
You may be just doing it wrong. This is a badly coordinated engineering test with a stand-alone entertainment grade
headset microphone and separate
stereo headphones. I'm using a small sound mixer instead of trying to force the computer to do everything.http://kozco.com/tech/audacity/clips/De ... ilyCut.mp3
I have two USB gaming headsets and the voice quality is terrible.
Audacity has no good way to split up microphone and headphone in a USB headset. You live and die by the driver software and sound management tools. It's actually worse in Windows 10. Your microphones, headsets and software have to say they work with Windows 10. Just "Windows" isn't going to do it. Win10 is a new system and software has to be written for it.