Hi,
All this depends on your circuit. You should give at least your example circuit.
* Supply voltage?
* output current? source only? or sink too?
gain: How much gain do you need? What is the input voltage? I estimate it should be a unity gain buffer, am I right?
BW: For me a reference voltage could be considered to be DC. Now it depends on the load current frequency, specified load capacitance .. and how much output voltage error is allowed?
PSRR: What powersupply fluctuation do you expect?.. and how much output voltage error is allowed?
CMRR: Does the common mode voltage fluctuate? I don´t think so.
PMOS/NMOS: I´m no expert, but i think this depends on common mode input voltage.
Klaus