It depends on what you want to achieve. Setting up_threshold at 90 is good for battery but bad for performance. The same for sampling_rate. "dirty" values are also very device specific because - in simply words - it configures how often RAM memory is kept and written to nand memory. So as long as things are saved to RAM your device behaves faster, but when they are about to be saved on nand then the more memory you saved in RAM the longer the process will take and the longer your device will be under less or more heavy load.
Also in Android the more free memory - the slower the system is. So it's NOT about saving the memory (as most so called "performance" scripts does) but about using all possible resources.
My advice - don't play with it
