Q2 is a unity gain buffer. Any reasonable gain transistor should perform about the same in that spot. No adjustments are necessary. But if you do want to adjust the gain then the emitter resistor (10k) would be the one to adjust. On the other hand Q1 is configured for a gain of 66 assuming the transistor has infinite gain. So to the extent that the actual transistor gain (hFe) is not infinite, that reduces the circuit gain to something below 66. Again it is the emitter resistor that adjusts the gain.