Can it really do that? I thought the chip was stuck with either one or the other. Like if you choose efficiency, then you're stuck with it, and not something that can be switched back and forth. Unless that is why the system is called Switch.
There is one choice you can only make once when you create the hardware.
That's die size, and it's a trade-off between cost and performance/efficiency.
Dynamically, you can change the clock and voltage, which is a induces a tradeoff between performance and power consumption.