or more specifically, low rpm power vs high rpm

Cam size, intake port cc's, and somewhat intake manifold design.

Mainly camshaft. You can have identical engines with different cams. The powerband will be determined by the cam grind. Other things like heads, intake etc will only compliment or hinder the amount of power the engine will make in that powerband.

A typical street cam will have a powerband in the 1500-5000 range because that's where it normally operates. A street car doesn't need a powerband that starts at 3000 rpm while it always drives around under 2000 rpm.

A race car like mine has a powerband that starts around 4500 rpm and peaks around 7800 rpm. Going down the 1/4 mile where my engine normally operates, the engine rpms stay at peak HP in the 6500-7500 range.

Advancing or retarding the camshaft can move the powerband up and down slightly in rpm.