overlap silent video with video and audio
What you want to use to control where clips are placed is Source Patching and Track Targeting. Those are two of the small indicators to the left of the timeline tracks. Track Targeting has a couple of functions, in general it controls which tracks varied editing operations can affect. For example, if you paste clips from the clipboard, the pasted video and audio will be placed on the lowest active (targeted) audio and video track respectively. 

If you want to control where the clips from your Project Panel go, you can use Source Patching instead. Only one audio and video track respectively can be the activated at a time in the Source Patching column, and those will be the tracks that new material is placed into by default.

You can find more info on that on the Adobe support pages.