Re- differences between the way android and ios work...android is dynamic, meaning, your icons and browser page are drawing as you are scrolling...I'm not too hip on the technical aspects but android has opted to give you more "live" even if it means that there is a bit of lag while all elements are fully drawing. That's why a faster or overclocked cpu or gpu may help that process go faster. IIRC, ios takes a different approach and the screen won't actually open/refresh until all elements are drawn, so it's static. It still might happen pretty fast, but that's why it scrolls so smoothly. I don't think either is better or worse but it depends on what you want.
Re- the status bar and overclocking the cpu, go into settings--interface and performance, as well as all settings for that matter, and just explore. You can't really hurt anything so try out some different settings, see what does what.
Re- EOS nightly build102 versus EOS 2.0.0 stable rom--they are largely the same, but the 102 nightly build has a newer kernel, among other things. V 2.0.0 is stable and is wonderful. That's why it was released. The nightly can sometimes be buggy but for those of us that crave constant tinkering, nightlies are the way to go. I doubt that you would experience any noticable change if you were to go back to V 2.0.0, but you would know that it was deemed bug-free before release, and that may be important for you as you get to know the Xoom.
Re-- customizing--the Xoom is very customizable, if anything, you may have too many choices. Go into the Themes and Apps section and you will get a taste of what's available. That's one of the great things about this device, and android in general...you can really make your device your own.