1) When do you use a low impedance mic vs a high impedance mic.
2) Is Prologue 14H suitable for vocal performance?
1) The choice of impedance is determined by the input specifications of the device into which you connect the microphone. The device might be: a mic mixer, a tape recorder, a guitar amplifier, a computer sound card, etc.
2) Yes. It is an entry level product. It is perfectly adequate for a beginner or for use in the home.