Be careful - there are SOME cases where there CAN be a difference between ripping at 30x to ripping at 8x....... It will all depend on the condition of the disc you are ripping from. I've done many tests in the past using CDDAE and its built-in error verification tool with yellow and red graphs representing errors in the comparaison.
I have found that on some audio CDs, yes original, pressed CDs, when ripping at 30x and running a compare I would get quite a few yellow spots, which represents errors..... The fewer these errors the less likely you might hear them, however, for some low volume or some type of songs like classical you will notice pops and other noises. Otherwise, if a disc is not damaged, scratched or dirty and in healthy condition there should be no problem at all extracting at the maximum speed your drive supports.
You can run tests on your own. I've taken many health Audio CDs (originals) and ripped them at 30x and used the bit verify function, all turned out error free..... Done the same rips at 4x and 8x, and binary compared the WAV files, they were identical bit for bit......
My recommendations - if you are aware that the Audio CD is in bad shape (scratches, dirty, etc....) it is best to at speeds lower than 12x, I'd say 8x....otherwise no problem.
As to BURNING an Audio CD, I would not go higher than 8x for burning an Audio CD-R. No matter how hard you try your burnt audio CD will never be bit for bit identical to your original, but usually it comes pretty close with very low errors, you want to keep it that way.
EAC (ExactAudioCopy) works differently and is actually much slower, but provides a more accurate extraction to come as close as you will get to the original.
Ã€s far as C1/C2 errors, on a good media you DO NOT want to see ANY C2 errors..... As to C1s, the lower, the better, usually not exceeding 50 (not the total) - normally good quality burns would be in the single digit range.