WilliamLi0623 I would recommend you to use taxonomies, and use tags in a less specific way, taxonomies allow you to do that (let users create their own taxonomies), and also because they offer a more scalable way to manage the free creation of tags/taxonomies, is not a good idea to abuse tags because they are very heavy, behind each tag there is a complex permission system that regardless of whether you use it or not is there, and with a free creation of tags can lead to performance issues in the future.
