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Shutters on a fan aren't great because the pressure drop at the inlet consumes some of the power you just saved. My preferred method for alternator cooling would be an undersized fan (half the flow) with a supplemental electric fan for low speed.
Fans and coolant pumps consume power proportional to the cube of rpm, so those are the biggest gains, and they're big enough to be noticeable even for street driving. Power steering is inefficient because steering assist is not needed most of the time, but the flow control valve built in means parasitic losses are almost linear, proportional to rpm.
My thinking around accessories is underdrive them a bit, and don't think too much about it, with the exception of the cooling system. On a race car that's always running at high speed, you can underdrive everything more and avoid prolonged idling. For a street car that's usually running at low engine speed, the extra hp lost at high rpm isn't usually a concern.
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