Pantheon's Arch Linux support is not finished - I'm pretty sure you can't run Pantheon on it. However, on Gentoo I'm sure you can. Besides that, we do offer so

Pantheon's Arch Linux support is not finished - I'm pretty sure you can't run Pantheon on it. However, on Gentoo I'm sure you can. Besides that, we do offer some customization, you just have to use dconf-editor to change the configuration keys and not a GUI for several things. And there's also "elementary Tweak" which adds even more configuration.