etzeppy wrote
1. Is there a reason to keep power to the buffer all of the time? Does switching power off and on with the foot switch introduce issues?
2. If switching power does not introduce issues, why not use that method with other circuits too. Why keep power constantly engaged?
The 3PDT engages the ground in the sense that it makes the ground -> LED -> +9V circuit when the wah effect is engaged; The wah circuit itself is permanently connected to the power/ground loop whilst the circuit is in operation, although the input socket of many effects will use a stereo jack so the ground is lifted when the input jack is removed to preserve battery life.
The audio part of any circuit should be permanently connected (albeit with the jack socket defeat outlined above) to avoid the loud pop/click that would occur if power/ground was switched during operation, and to avoid the slight delay as electrolytic caps charge up.