there are three types of spark plugs that i know of off the top of my head.
Copper plugs, double platinum, and iridium spark plugs.
spark plugs don't have any relationship with octane ratings that i know of.
Copper plugs are good with cars that have cap and rotor set up (one coil feeding all cylinders) like all the old cars do.
Double Platinum are need in applications were the waste spark (one coil feeding two cylinders) setup is used.
Iridium plugs are usually need in setups where the car uses coil over plug (c.o.p.) these spark plugs are expensive and can be replaced with copper plugs. but the Iridium will last longer.
other than that most auto parts stores will help you out with the recommended factory spark plugs. correct gap and everything.
octane rating has to do with compression ratios and ignition timing. most drivers on the road don't have to worry about octane rating, everyone can use cheap gas. only people driving old cars like my old bug with no computer controlled timing have to worry about that math.