I usually don't let FCPX analyze anything while importing. This takes extra time, and you can still do any analyzing on a clip by clip basis or on a group of clips anyway once you have imported the clips.
Auto balancing is what it says: it's an automated feature that may (but not always) produce a proper color balanced shot. The analysis is non-destructive: you can always deselect it in the Inspector while you are editing (Video tab > Color: Balance). I rarely use this.
You can always analyze and fix audio problems when you hear problems with imported clips. Again no real need to do this while importing. Select the clip in the Event Browser (or on the Timeline) and go to Inspector > Audio tab > Audio Enhancements. Click the little right arrow to reveal the Audio Enhancements window.
When you have stereo audio that you want to configure as dual mono channels you do this after importing: select all the stereo clips In the Event Browser (or on the Timeline) and in the Inspector > Audio tab > Channel Configuration change Stereo to Dual Mono.
Remove silent channels is one of the useful things you can do while importing. Although you can easily deselect silent tracks on the timeline or in the Events Browser as well.