OK, so if I don't have it completely backwards, I understand that the higher the preout voltage, the lower the gain can/should be set because the amp doesn't have to be as sensitive of the incoming signal - so the amp can put out full power with the lower gain.

My question is since the gain isn't set as high, is the amp drawing less current because of it? Or is it drawing the same amount of current as a signal with a lower preout voltage and higher gain setting? Just curious.

The same.

The gain is the input level matching circuit. Higher input = less gain to match the input level that the input stage is designed for.

The output stage is what uses/makes all the power (and heat).