on a 2x10 you should be able to get away with any ratio. for a triple there is still a good amount that is acceptable as far as chain wear is concerned. As for cadence: it was my understanding that the high cadence allows for better muscle oxygenation because the muscle is under strain for less time before it is released allowing the blood vessels to push more O2 where it is needed the most. To that extent it is supposed to reduce the lactic acid buildup. so... faster cadence = better.