Ah no worries.
For future travellers, I think something like this would do it:
-- [params]
-- date :start_date = 2024-05-01
-- date :end_date = 2024-05-31
-- int :top_x = 10
-- int :column_sort = 2
SELECT
p.user_id,
COUNT(*) AS "Topics+Posts",
COUNT(*) FILTER (WHERE p.post_number = 1) AS "Topics",
COUNT(*) FILTER (WHERE p.post_number <> 1) AS "Posts"
FROM posts p
JOIN topics t ON t.id = p.topic_id
WHERE p.created_at::date BETWEEN :start_date AND :end_date
AND t.archetype = 'regular'
AND p.deleted_at ISNULL
AND t.deleted_at ISNULL
AND p.post_type = 1
AND p.user_id > 0
GROUP BY p.user_id
ORDER BY :column_sort DESC
LIMIT :top_x