You can also use data explorer for your other questions
Is that about what you had in mind?
SELECT
c.id AS category_id,
COUNT(DISTINCT pl.post_id) AS translated_posts,
COUNT(DISTINCT pl.locale) AS languages,
COUNT(*) AS total_translations
FROM post_localizations pl
JOIN posts p ON p.id = pl.post_id
JOIN topics t ON t.id = p.topic_id
JOIN categories c ON c.id = t.category_id
GROUP BY c.id, c.name
ORDER BY total_translations DESC