LC, I am not trying to be a ******** but:
Octane only refers to a fuel's (gasoline) ability to resist detonation, nothing else.
Burn rates are the same, specific energy output is the same. Volatility is a function of the vapor pressure, volatility is independant of octane.
Does higher octane gasoline make more power? Yes, assuming you take advantage of it. Increased compression and advanced spark timing increase overall cylinder pressures during the power stoke thus extracting more work from the same amount of fuel. The amount of energy (114,000 BTU/gallon) remains the same, but due to the construction of the Otto cycle engine you can extract more work from the same amount of energy.