How to Change Appended Videos Default Audio Track

I have two videos that both have the following audio settings:

PCM Audio (Default)

AC-3 Audio

When I append one video to the other and change the source videos default audio track to AC-3, how do I change the appended videos default audio track to AC-3 as well?

The audio “Default track” flag setting for the appended video is greyed out. Which means the source video’s default audio track will be AC-3, and the appended video’s default audio track will be PCM?

How will that affect playback, will the audio switch from AC-3 to PCM when the appended video part plays, or does the appended video’s audio default to the same as the source videos default audio track?