A common request from new users is how to know which plugin is safe to install or not. In fact probably all of them are safe but as a new user that's not necessarily easy to know. So to help with this, the next version of Joplin will support recommended plugins - those will be plugins that meet our standards of quality and performance, and they will be indicated by a small crown tag inside the plugin box. Recommended plugins will also appear on top when searching.
For now, since we don't have a review process, the recommended plugins are those developed by the Joplin team and frequent contributors, because we know those are safe to use.
Later we might have a review process and add more recommended plugins. That being said, in the meantime even if a plugin is not marked as recommended, there's a good chance it is still safe and have good performance too. Often you can search for it on the forum and if it's active with many users commenting, you're most likely good to go.
But if there's any doubt, the recommended tag is a good way to be sure.