YTMP3 Blog
MP3 Bitrate Guide: 128, 192 or 320 kbps
What MP3 bitrates change, with file sizes for each option.
MP3 vs M4A: Which Should You Download?
When to choose MP3 and when M4A is the better file.

What Audio Quality Does YouTube Actually Use?
YouTube's audio codecs and why they limit any MP3 made from them.
Where Downloaded MP3 Files Go on iPhone and Android
Exact places to find a downloaded MP3 on your phone.
Why a YouTube Link Fails to Convert
Common converter errors and the fix for each one.