Yes, it is possible to use a potentiometer to adjust the differential gain (AVDIFF) of the MAX4063. The maximum characterized gain is 200V/V with a gain setting resistor (RG) of 1.01kΩ.
MAX4063
Production
The MAX4063 is a differential-input microphone preamplifier optimized for high-performance, portable applications. The device features two selectable inputs...
Datasheet
MAX4063 on Analog.com