Advance sort of linked to peak cylinder pressures.
You want the highest "mean" pressure without supersonic flame fronts.
Higher the compressed mixture is BEFORE spark, (all other things being equal), the higher flame front speed.
BTTT, tolurine, analine and don't forget mind your paint, and fuel system seals, a dash of methanol helps keep flame front in check.
Only for the brave get it wrong, time to get the spare motor fitted