So, neither of these solutions is actually a solution.
Consider: you record a video from a video camera that gives you a nice sharp video along with its annoyingly bad audio. Call this Video A and Audio A. You add a single .mp4 file that contains both of them, linked. At the same time you record beautiful bell-clear audio via a microphone into an audio file. Call this Audio B. You add this to your project as an mp3 file. What you want on your output is sharp video (Video A) and bell-clear audio (Audio B).
So, you
1) Drag the mp4 clip into your sequence.
2) unlink Audio A from