Ideas for managing tags

I'm currently writing a messageboard with tag based discussion.

My current plan for implementing tags is that the admin/moderator selects a handful of tags, and users can freely apply them to new threads. This seems like the best strategy for reducing tag spam (useless tags, mistagging, etc). But I'm thinking that maybe allowing users to create new tags with a limit of 3 tags per thread may be better.

How would /prog/ approach this?

https://github.com/FrozenVoid/Algorithms-DB/tree/main/Order/Sorting/Tagging/Tagscore/Tag-category

Add voating for new tags. User adds a new tag to a created thread and others can upvoat to make it a global tag, or downvoat to remove.

dicks out for Harambe

Looks like an interesting project.