Higher octane fuels actually contain marginally less energy. They also burn slower.
Octane is a measure of resistance to knock. That is all it is. More octane does not equal more power or more energy. Engines that are more likely to knock - high compression, high boost, and so forth - can benefit from higher octane fuels.
In an engine that would otherwise knock with more advanced timing, higher octane allows more advanced timing without knock. This generally applies to Mark VIII engines - but only up to a point. These engines were designed for premium fuel, and can benefit from those fuels by advancing timing, or rather, not retarding timing. If you want to know if your car could use higher octane, run an autotap or similar and look at what the knock sensors are saying.
As a general rule, the car will make the most power with the lowest octane fuel it can safely run.
If you want to run higher octane, look into E85. It's about 105 octane and a lot cheaper than race gas. Everything in the fuel system has to be safe for alcohol, though, and you'll burn about 30% more fuel because ethanol contains less energy than gasoline.
Too high an octane can cause damage to an engine, because the fuel is not done burning when the exhaust valves open. You lose power and put your engine at risk.
Lead probably won't hurt your engine but will kill your cats and your o2 sensors probably won't like it.