This is actually what I replied to a person who was wondering what to write for the Block Party organized by Kelly Anne Blount.
The first time I was around the block, I wrote a sneak peek from the next book in the series I was uploading on Wattpad.
End result: I got comments mostly from the people who read the series.
The second time, I posted writing and wattpadding tips.
End result: I got comments from other writers.
What I concluded from those two parties is that whatever you write and however you write it (long, short, simple, fancy), there will be people who are interested in it and there will be people who will skip it. That’s why I’d advise you to write whatever you are in a mood for and make it as long as it needs to be. If you end up with 1K words, that’s fine; if you end up with 2K words, that’s also fine; if you end up with 10K word, some people will be put off by the length, but if the post is good, they’ll still read it.