The scene is very active, any new company these days will always brand themselves as a "startup" no matter how they function behind the scenes. So alot of "false advertising" when you postulate, "we're cool and all, we SOMETIMES allow a day of remote work a week" and typical bs like that.
Your french will need to be good, because it has been proven time and time again that we are bad as flip at learning languages and if you watch statistics online you'll see we're worst ranked in the entirety of Europe in languages.
Used to be that there were some "startup heavy" districts inside Paris, still is the case, but now we also have the brand new "Station F" that sells itself (or rather Macron sells as) the next Silicon Valley of Europe.... Never heard that anywhere...
My SO is currently in internship at station F and she told me the turnover is pretty crazy, it's more of an incubator that helps new startups get on their feet, so they'll probably stay around 6 months and then move far away to get cheap offices. Also apparently their selection process is run by old investors that have no idea what they are doing and if you simply sell your sh#t product/service well enough you'll get in. From what my SO told me about 50% of the startups over there are your typical "marketing" based "services" that sell you vaporware and invest 99% of their revenue in better "packaging" and what not, if you know what type of "company" I'm talking about...
Last thing, you'll probably get a good pay since your resume mentions the words "worked at Silicon Valley", but from my experience, every single HR will try to f#ck you over when you are being hired, so you better be a tough negotiator. For reference I currently earn 30k eur (about 21k after tax) a year as a junior (2 year xp) full-stack dev (mainly node, php and alot of sysops)
I'd resume by saying that overall, startups in Paris are more akin to those in SF than the Silicon Valley if you know what I mean. That might be your sort of thing, but I'm more of a "I want to build the future with my new js framework" type of guy... So have been considering moving out of France.