all sorts of factors determines octane needed to prevent pre detonation. compression, timing, pipes, etc. but for the most part anything over 150 usually need higher than 91 octane.
stock motor with off the shelf domes, standard mid range pipes with no added timing will usually do fine on 91 even with 150lbs i have done it, but doesn't mean it will work for everyone. you mentioned high hp bike. i don't know what your idea of high hp is, but i would suggest talking to a builder about your end goal power wise and let them guide you to what you will need. some builders have certain setups down so well it is generic. x base gasket, x domes, x timing etc.
short story is no one says compression ratio because in the car world the piston can determine the end psi. for the most part banshee pistons are all the same dome profile and compression ratio. hope this helps