What are these things you want to customize? Main reason I wanted to customize stuff when I used Linux was that so many defaults sucked. I don’t feel that problem on Mac. I change my shell, my shell font and color scheme. I toggle on showing filename extensions, and a couple of other Finder modifications. Change scroll wheel direction and remap my caps lock to escape.

That is pretty much it. I find that Mac OS for the most part gets out of my way. What else would you really need to change?