The message regarding plugin support is most likely unrelated to any microphone issues.
You'll want to make sure the "Enable Plugin Support" option on the "General" tab of the VoiceAttack options window is enabled (checked), as the log message mentions.
If there are still Oculus devices displayed by Windows, the drivers for that device are still installed. If you have no further need for the Oculus software, you may want to uninstall that (which should also uninstall the drivers).