1. Filter design starts with the specification, pass- and stop band requirements, resulting filter order. Sallen key is surely a candidate, MFB may be advantageous for fully differential implementation.
2. Not particularly. Anti-aliasing filter requirements can be quite different. Low order and relaxed spec for oversampling ADC, high order and tight spec for signal bandwidth near the Nyquist frequency.
3. Rule of thumb says GBW >= 10* filter frequency, at least for low and medium pole pair Q. Filter dimensioning may need adjustment for finite GBW, good filter design tools will do.