[rotrex]

It depends. Given a high octane base fuel, enough water meth, effectve nozzle location and a well designed combustion chamber/piston/squish etc. you might hit MBT before any knock occurs. If you plainly map to the knock limit, you might seriously overload your engine.
Most engines today run a rather high compression ratio and often hit knock before MBT.
My strategy (supercharger) was always to start with reasonable low timing, get the AFR you want and then increase timing step by step and feel if power increases. If either power does not increase anymore or knock occurs, you have hit the limit.
On a dyno, you can see rather small changes. The butt dyno works well enough for street use. If you do not feel any increase anymore, it is not relevant anyhow.
In terms of amount of spray, I found with my latest direct port nozzle location right before the fuel injectors on the top side that the more flow I dailed in the more extra power I was able to extract after adding timing. When I improved squish I found no more improvement past a certain amount of spray despite a increased compression ratio. I seems I am no longer knock limited. :-)