Adding tags is always safe. Renaming a tag is also safe. Deleting a public tag is the one change worth checking with support first.
Deleting public tags. A page or menu link on your site may point at a public tag’s collection page. If you delete the tag, that link is left with nothing behind it. Before you delete a public tag outright, ask support to confirm that nothing links to it.
Leftover filter entries. When a tag is renamed or emptied, an empty leftover filter entry can remain on your website. Support can clear it.