Author Existence Failure: Yamaguichi died on April 4, 2013, after losing a two-year battle with cancer, and with the last two volumes still incomplete, and many questions regarding The true nature of the Void, Brimir, and the origin of the conflict between humans and elves which were meant to be addressed in the final arc, forever unanswered. The anime's 4th season is as close to a closure as we'll ever get.
In the English Dub, Louise, Tabitha and Kirche have the same voice actresses as Nanoha Takamachi, Fate Testarossa and Arf, and none of them try to change their voices much. Granted, none of their characters are different from their others... Except for Louise to Nanoha. Incidentally, that part's hilarious to listen to when Louise really gets going.
Official Fan-Submitted Content: Just like in the Spanish-language dub of The Sacred Blacksmith, Louise and Saito's voice actors in both the Mexican and European Spanish dubs were selected by the fans. In both versions, rather than using well known voice actors, both dubs used newcomers for both characters.
In the English dub, at least, Tabitha and Kirche, the quiet young mage with serious parental problems and her busty, energetic redhead best friend, are also Fate Testarossa and Arf... a quiet young mage with serious parental problems and her busty, energetic, redhead familiar.