There are a lot of scripts for optimizing Android. Pikachu made a thread describing them:
Android Optimizations
But it is a lot to read, and I will try to explain the AddOn features with simple words.
1) Low Memory Killer:
Android keeps all apps in memory as long as possible. If you start an app, that is already in memory, it starts very fast.
The Low Memory Killer will remove apps from memory, if there is not enough memory for the current app, but this will take some time, the app "lags".
The xx-mb is the free memory, when the Low Memory Killer will begin to remove apps from memory.
32mb-multitasking: if you start a lot of apps parallel and want to switch very fast between the apps.
92mb-chainfire: this is used by the minfree tweak from chainfire in tweaks app. This option is for using an app exclusive, no multitasking.
48mb-default: this is the samungs default, a good compromise allowing a bit multitasking and not so much lags in big apps like 3d games.
64mb-bigmem: this option tries to use the extra mem provided by the bigmem kernel to reduce lags.
So it depends on your phone usage, what is best for you.
2) Hard to kill Launcher:
By default the launcher is an app like every other app for the Low Memory Killer. If you start big apps, the Low Memory Killer will also remove the launcher from memory. You can see sometimes, that the launcher is black for some seconds and than displaying the app icons again.
If you enable this option, the launcher gets a higher priority, and will not be removed so easy.
So if you had already the effect that the launcher is started again, and you don't want that, you can enable this tweak.
3) SDCard read ahead
If bigger files are read by apps, there is less overhead reading them having greater read ahead config.
If apps read a lot of small files, there is less overhead reading them having smaller read ahead config.
128kb-default: This is samsung default for all mounts. a good compromize.
256kb-64kb: This increases the SDCard speed, as it uses a smaller read ahead for the kernel config files, that are mainly very very small. And a greater read ahead for the apps, and apps data that are mainly bigger than 128kb.
3072kb-chainfire: This is the setting of SDCard tweak from chainfires Tweaks App. It is a bit too high, as there are also smaller files.
Some people prefere 512kb-64kb or 1024kb-64kb.
So you will see the difference of SDCard speed with Media Scanning, load time of apps.