I'm not a litterary person, so I guess that I would not be significantly be more eloquant in French rather than English. I've been told I have a pretty decent idiomatic sense of this language for someone who basically self-tought after endless hours of binge watching US films/movies.
The one thing I lack would be a native vocabulary, but I think I'm fairly familiar with nowadays mainstream slang and I guess that with an unlimited access to information, I can fetch any required new word I'd need. My true Achille's ankle would be the mastering of specific English ponctuation.

Providing one has reached the stage of being able to think in the targeted language, I guess the difference between mother language and another fades away.