The reasonable answer is there are no special settings for music recorded from vinyl. Converting to mp3 will 'reduce' the audio quality. Choosing decent encoding parameters will likely make the reduction inaudible. From the information in the posts specifically about optimized presets, one might reasonably conclude that most people will be satisfied with the --preset standard or --alt-preset standard, depending upon which version of Lame one has loaded. If your ears tell you otherwise, try the next step up.
It's not exactly free but
http://www.delback.co.uk/wavrep/ is inexpensive and very good if you are working with 16 bit files at 44.1kHz or 48kHz. Being shareware, you can play with it. I think both Audacity and Kristal are free, but I don't know how many cleanup tools they have. Goldwave is also inexpensive. The better programs are going to cost you. If you are really interested in results, they are worthwhile. Start with the trial download of Audition from Adobe.