You can't really speak in generalities when it comes to race fuels and engine management systems these days. Typically old school leaded race fuels have very different specific gravities and end point temps. This usually means you put it in your tank and the tune becomes richer. You make power by leaning out the afr beyond what you can run on low octane and you advance timing beyond what you could normally run.
With unleaded race fuels usually its the same afr when you start but again you use the same strategy as the leaded fuel.
Now oxygenated race fuels are the rage and they can run leaner when filled in the tank and because they cary oxygen it will make more hp with no tuning...about 4 to 6%. These fuels make more power on the rich side vs. The lean side so they can sometimes have really good results on a factory tune.
Engine management systems vary in their ability to advance timing by sensing knock. Subarus have a abnormal amount of ignition advance available on top of the base timing map along with an agressive nature to seek knock and then back the tune off. This is why we sell so many engines
Other more logical ems systems only have enough learning to take advantage of say 93 octane.
It has already been said but the only way is to either log the timing curve or put it on the dyno with race fuel and wait for it to learn.