Hi Diego,
We had similar problems as our first language was spanish, then we added english and migrated the website to a new WP. The dev created an /es/ directory. We couldn´t avoid 301 redirects. Anyway, the only thing we have lost was the social media share counter. In terms of organic traffic we saw no impact (overall impact was positive because we started creating more content since then - but this is another story). Actually if I had to do it again, I would keep the original URL as it was and only create the /en/. Someone else has another opinion?
For your 2nd question: Your target user would be an english speaker living in France?
If so, you should use hreflang:
Kind regards,
