It's up to you. Which such a long article if you focus in the right direction, it could be driving visits by itself.
Not the whole point of building a PBN to boost yours results from a minmax optimization of your time perspective but still legit.
Higher word count helps Google with relevance, as long as it's not just fluff. Write as much as you can about the topic within reason of course. Some people don't want to read a whole articles just want the main information