When it comes to multisite Drupal installations Domain Access is my module of choice. For multilingual sites i18n is the way to go. Bringing those two rather complex modules together can be quite a hassle. In order to set different system settings (such as default front page, site name and slogan) per domain and per language you need to install Domain Variable. Unfortunately there’s no real documentation to tell you that Domain Variable will not work as expected as long as you’ve got the Domain Settings submodule enabled. As soon as you disable that you’ll be shown those per domain and per language settings on the forms you’ve enabled inside Domain Variable settings.