Ok....how can you say you understand what it's all about....but ask 'what you're really doing' when changing a particular number....that kind of contradicts the previous statement.
but why can't you just set it for the best timing every time?
you DO set it for the best timing...that your RAM is capable of all....cheap RAM isn't going to be able to run the same tight timings as good RAM.
By the way the number you are changing is more than likely the command rate. 1T will offer more performance than 2T, but when going for high OC's, 2T is necessary for stability.
scroll down until you see DRAM TIMINGS