I have a different advice for beginners: don’t worry about creating or optimizing “systems”.
Be playful!
Hashtag are fun because you can sprinkle them anywhere. They are easy to add and easy to remove.
Of course you could build immensely complex systems with nested tags and controlled vocabularies and tags in frontmatter and tag pages and links as tags and tags as links and what not.
But you don’t have to.
You can also take a lighthearted and playful approach.