Thank you.
I use Screenflow, and it'll capture your monitor video, along with desktop/game audio, and mic audio. There is also an option for capturing webcam video, and it's audio as well.
Video and game/desktop audio are in 1 editable track, and microphone audio is on it's own. Allowing you access to both directly in Screenflow, which is also a pretty darn nice editor in and of itself. It actually has better zoom transition/functions and keyframing that FCPX, as it was originally made for screencasting.
Also there is no noticeable performance issues, this was with a previous upgraded 2009 Mac Pro, and a 2012 Mac Book Pro prior to that.
For recording using a separate scratch drive is very important, especially a fast one. As you'll be constantly writing data to it.
I hope that helps.