I haven't seen a piezo mic since about 1962. It is completely different to an electret mic. The resistor R4 that powers an electret mic is not used with a piezo mic. The electret mic has a Jfet impedance converter inside for its fairly low output impedance but a piezo mic has a very high output impedance that might need a preamp with a very high input impedance.
A piezo mic might have many strong high frequency resonances.
A piezo mic might have many strong high frequency resonances.