In general, the creator of a video can choose any combination of video-quality and audio-quality.
In practice, persons who know what they are doing, and also the automatic engines of YouTube (facebook should be similar) that create different quality versions of the same video, have profiles, where the quality of video and audio is linked.
So yes, higher quality video comes with higher quality audio on YouTube:
360p videos have 96 kbps audiotracks, while 720p videos habve 192 kbps audiotracks.
192 kbps is way better than 96 kbps. I don't have a 1080p-video here to check, but I remember that audio-quality reaches its maximum at 192 kbps. So 1080p-videos will not sound better than 720p-videos. For me, the sweet spot is 720p.