Global spark is spark added after every adder and retard has been taken into account. It is spark added or taken away from your final spark calculation. IT IS spark advance just done in a different way. Spark advance is usually done based on load or rpm but global spark is done everywhere.
Going from 91 to 92 octane in my opinion is pointless. Octane ratings are not accurate anyway so 91 could actually be 92...or even 90 etc. In general, increasing octane allows for more spark advance by 1 degree per octane level. Meaning 92 would tolerate 1 additional degree over 91. That is not a rule though.
What FSW offers for thier tunes you would have to contact them on that.
Thank you! It's a great simple little thing that goes a long way. I've been hearing both sides about wheels or drop first. I've heard that it's better to get the wheels first to see how low you can take it.