"Under Promise Over Delivery" is always better than the other way around. Breaking the reward pool into fix and variable would be a good way to go. So that as you post an article and as people interact with your post you know what is the assured sum. By the end of the week earning a bonus will be like an added cherry that you don't count on but would be like a pleasant surprise.

Content creators will always need some assurance so that they don't think twice before investing their time and efforts into creating content.