A hard requirement might be:
being available at a fixed time and place;
holding a licence needed for the work;
meeting a genuine minimum age;
having the right to work through the stated route;
being able to complete a required physical or technical task.
A preference might be a style, background, level of experience or way of working that helps the client compare people but does not automatically rule everyone else out.
Hard requirements should be visible and used only where they are genuinely necessary. Protected characteristics must not be used casually to narrow access. Some castings may need a lawful and genuine role characteristic, but it should be reviewed and explained properly.
The Connect does not rank people by follower count, school or paid tier.