Best way to organize multi-language sets of articles

Hi all.
I have different website versions with their own sets of translated articles and list of languages (shared across all websites). So Article1 may be presented in EN website version only
All articles have same fields (date_post, author, preview_text, detail_text etc). same document ID also

Each article for each country-based website is translated for all languages
I want to search articles by user-defined languages: so website EN - search by fr_FR

It's hard to decide: One Language per Document, One Language per Field or Mixed-Language Fields

Did you read ?

i did. But still cannot decide for different content with different langs