The stars represent best chances of a successful connection & downld. Aiming for hosts with 4 stars (& multiples of hosts under the # columns) will help you to get fast connections rather than ones that immediately go to need more sources.

The CD quality argument is a very tentative issue. I've read where some people claim 128 kbps is cd quality. But that's really a load of ....
mp3 bit-rates allow up to 320 kbps (there are some rare programs that allow slightly higher than this but rare for people to share these. Most players wouldn't play them.) m4a or mp4 audio is similar. But within the m4a mix is apple lossless which uses the same format. So if you see an m4a file that's higher than 320 kbps, you know it's apple lossless & is equivalent in quality to aiff or wav or cd quality. Lossless formats are called that because despite compressing the file size, they don't throw away any information. Whereas mp3 & m4a are both lossy formats where they throw away information to help reduce the file size. The lower the bit-rate, the more information they have thrown away compared to the original CD. I hope this helps for your understanding. I always aim for 192-320 kbps. Likewise most of what I encode to share is around the same.

But keep in mind that mp3's use more than one technique to reduce file size. One of them is to filter out frequencies above 15 KHz because most adults are generally unable to detect frequencies above this. In practice, the quality of an mp3 not only depends on bit-rate but the quality of the encoder & the settings. eg: A 128 kbps file with a high quality encoder can sound better than one encoded at 250 kbps with a cheap nasty encoder.

Diferent types of music or particular songs reduction of quality V's reduction of bit-rate may be different. Some songs don't sound very good when bit-rate is reduced too much, whereas some soudn fine! It depends on their frequency make-up/design throughout the song & how well the encoder could handle it.