As far as I know, OBS does not allow you to save your audio separately from the actual footage. Which is a shame, because it'd be really nice to have separate control of the gameplay audio and your voice, so you can make adjustments as needed. What most YouTubers do, but it's so inconvenient, is record their voice with Audacity or record their facecam separately and then edit it onto the gameplay footage. I know it's a pain, but it's either you deal with what you have, or you use multiple tools. My nickname for OBS is 'Oh, BS' because it's a software that does exactly what I need it to do, but there's a lot of room for improvement. And what do you mean by not saving? 'Encoding overloaded'?