Well, I finished using my user but with a defined scope from the MCP settings (read/write on forum content) and edited tags or categories in hundreds of posts in less than an hour.
I thought about creating a specific user to limit access even more, which, trusting the Discourse team’s implementation, was unnecessary and more complicated than what I ended up doing.
Previously, when using API keys, the workflow was a bit different. I like this new approach and fully support this development 
Thanks nat for your patience!