Layout on vmax,theor
The equation between power demand and supply is reached at the nominal speed n0 and hence at the maximum hub power. With this layout, the theoretically largest possible speed is realized. In the range below the maximum speed however, only a relatively small excess power is available for acceleration, climbing, or headwind.

Overspeeding Layout
The nominal speed is exceeded before the point of equilibrium. The engine speed at the maximum velocity is larger than the nominal speed. In this way, a large amount of excess power is available in the maximum speed range. The theoretical maximum speed is however not achieved. The high engine speed at vmax causes a higher driving noise and greater wear. The engine operating point which is driven in this case is generally in the range of high fuel consumption.
The fourth gear of common 3-gear transmissions, 5-gear transmissions with the fifth gear in overdrive and the largest gear of sporty 5-gear transmissions in passenger cars are mostly designed based on the overspeeding layout.

Underspeeding Layout
The maximum speed in this case is achieved before the nominal speed, meaning at a lower engine speed. The theoretical maximum speed is not achieved. It is true that noise level, fuel consumption, and wear are lower, but since the excess power is smaller than the other two layouts, the maximum speed can only be reached slowly and drops steeply when upward gradients or headwinds are encountered.