Sorry, as I'm not quite sure as to the question, but I believe you're asking if a certain version is required to be used with the FFFox mod, and the answer is no. The FFFox mod will be able to be used with all versions once I finish up the DLC content. So it can be used on top of steam, Shadesishere's translation, prpr's translation, or even directly on top of the untranslated JP version. However, the way this game engine works, the translation will be overwritten by the mod, so no matter which version you install it onto, it will have the same outcome: my translation. WolfRPG doesn't support much compatibility in that department, so translations are typically all or nothing, which is why I'm also modding in multi-lingual support at the same time.
I'm focusing on getting the DLC fully set up before that, but it will be.
The mod supports JP internally. The game hasn't been fully converted into a multi-lingual compatibility yet, but most of the text has been converted, so if you go in game and switch the language, you'll find most of the game in JP, outside of H-scenes.