Window capture only captures a Windowed Game. Game capture will capture full screen games, But you may not see any activity on screen if you've alt tabbed to look at the preview in OBS. Some games don't stay active if they're not the primary window.
For mic, Make sure you have the proper mic device selected in the audio settings, Then adjust the volume slider as Terror provided a picture of as high as you need it. You will likely have to reduce the right slider, the system/game sound, to compensate, as that will almost always be louder. If push comes to shove, in the audio settings, there is a Mic boost, simply change its value in the audio options from 1 to 2.