I can't comment on the spark plugs, but I used the VP Octanium additive with very good luck on my racing motorcycle. That was a 12.5:1 pistons with milled heads. IIRC we were just over 13:1 compression.
https://vpracingfuels.com/product/octane-booster-vp-octanium/?c=367&
Didn't have detonation and that was on a carbureted bike.