noopener link relationship has nothing to do with the
nofollow link relationship.
On top of this, target="_blank" is also a security vulnerability. The new page has access to your window object via window.opener, and it can navigate your page to a different URL using window.opener.location = newURL. See About rel=noopener for a demo and explanation of the vulnerability.
Adding a rel="noopener" attribute prevents the new page from being able to access the window.opener property and will ensure it runs in a separate process. The rel="noreferrer" attribute has the same effect, but will also prevent the Referer header from being sent to the new page. See HTML Standard: Link type "noreferrer" for an explanation of this behavior.
And you're probably already aware that the
nofollow link relationship just instructs obeying search engine crawlers not to follow that link (and subsequently pass link juice - but there are other benefits).
It would be interesting to know what you're using the plugin for as it isn't advisable to
nofollow internal linkage and unless you're publishing a lot of user generated content, I doubt you're linking to places that you don't "vouch for" which is largely what the
nofollow link relationship is used for...