If you are fairly quick with the gain switches and do it at a decent moment, I've found the spikes can be cut from the wave fairly cleanly. I haven't had much luck using NR on them because they are 100% noise. I usually get the gain right so it isn't often an issue. An exception is someone like A. Escovedo who often comes into the audience and does a no-PA encore. That's a case where you have to significantly increase gain and point the mics in a different direction.. But since you don't know quite where the band is going to stand (and they often move before the second song), it can be kinda busy. So you're trying to be quick with your changes but not introduce handling noise, etc.
The AERCO needs 9 volts to produce 48 volt phantom.