A.) Recording you can go balls to the wall with resolution and bitrate. However, if you plan on streaming keep in mind that your viewer's internet have to be able to handle what you're outputing. I recommend 1080p60 @3k bitrate to keep your stream accessible.
B.) Voice volume @100%, game @75% and go from there. Put a noise gate filter on your microphone audio, default settings is a good starting point.
C.) Customize your alert volumes. Some streams have them ear rapingly loud.