Your oil choice does come into play depending on your ridding style. Castor bean premix should be used only by those who keep the throttle pinned and the engine in the upper ranges of RPM. Most riders have a common issue that castor oil products will leave a carbon buildup. That said, castor does a great job of lubrication, but as mentioned, the engine needs to be run hard and fast the majority of the time. Those who do study up on jetting, have a full understanding of how it works, and how to accomplish optimum combustion, will find that they have a much better running engine than their pals.
But you also have to realize that jetting correctly means jetting to the style of riding you do.
The 20:1 thing you heard is fine as well. Do I run at that rate? Only for break in. You have to remember that the point of breaking in the engine is all about "Expanding & Contracting". During break in, the engine needs more oil to lube the components. Shifter cart guys run 16/18:1 on a normal basis just for that reason.
More protection, and more power. The secret is to get the right amount of air/fuel into the combustion chamber when it fires.