--yes, the primary activities of Neurontin and Lyrica seem to be in the brain and spinal cord; both seem to act as GABA analogues in damping down the "runaway" firing of neurons that relay pain impressions. So it is not likely that their usage would greatly alter an NCS/EMG; indeed, neurologists certainly do these on patients who are taking these drugs. (Although, since the mechanism of action of these is not entirely understood, I would never say never.)

Certainly, many have complained about sleepiness and zombification on these meds, though many have also reported that some tolerance develops and the effects lessen in time. A lot also depends on size (I was able to tolerate 2700mg/day of Neurontin at my peak and still function mostly normally as regards mental acuity and energy, but, as I recall, I'm about twice your weight).

You can certainly experiment a bit with timing and dosage before you go in for the appointment, and see how that goes (and I suspect they will find osteophytic narrowing of the neural foramina, if my memory of you is any guide).