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The former (#threads/posts) may actually play against the latter (rank). By that I mean that if you rush to create large amounts of posts or threads, you’re likely going to lower the bar that one should set of trying to post something meaningful. Were it the case, this will play against ranking-up here, so it’s better to concentrate on the post’s content than quantity.
Although there are some time related limitations to posting, as per the formula quoted in the above post, one should rarely (*) encounter them unless he is spamming around the forum.
(*) Perhaps with an activity below 15 one may meet the cool down period message, but other than that, it should not really be an issue at all. Bear in mind though that the formula applies to a set of elements considered as one within the formula (posting, and searching the forum for example both reinitiate the "wait time" period).