IANAL, but French, working in the hedge fund industry since a while, and had numerous non-compete clauses over time. Also have had some experience negotiating then from employee and employer perspective.
The French landscape is a bit more subtle that what you mention here.
The first thing to understand is that everything in your contract is not always 100% legally applicable, and companies play with this idea. The local laws often dictate the overall rationale that a non compete can address, and companies play with that interpretation in the contracts (more on this with examples later) . In practice though, if there was an occasion to defend it in a tribunal, the company's interpretation would definitely be discarded. 90% of the non compete clauses that I had to negociate, either to get out of it myself, or as an employer to hire a talent, revolve around this idea: the clause is legal, but its not possible to enforce really, because the interpretation would be trashed in a tribunal. This is especially true in France where tribunals (prud'hommes) are free, and very favorable to employees. This is also true for other countries though, I had cases in Hong Kong where the landscape is quite similar.
Now, it is true that France allows for unusually long non compete clauses compared to other countries. More than 12 month would likely be trashed by a tribunal though.
As for the compensation of the clause, I feel like France is actually quite good. If there is a non-compete, then it is mandatory that there is a compensation, and in practice you can expect the tribunal to require at least 40% of the salary.
Note that the employee definitely has a great negociation capability here, because the company has to choose whether to apply the non compete up to 2 weeks after the departure of the employee.
That means, if you plan on doing something unrelated to your previous job, you can bluff a bit for the clause to be applied, and enjoy a nice bonus of 40% of your old salary on top of your new job.
If you plan to work for a competitor, here are some examples of what to look for in your non compete clause:
The French non compete has to be limited in space, time, and focus.
Limited in space means than it cannot be worldwide, there has to be a list of regions where you are prevented to work, and this list cannot be too long. I had an example with a clause that listed 10 major financial places (US, UK, Germany, etc) and actually the end result was that more than 5 countries and the clause starts to be pretty much unenforceable.
For the time constraint, the general assumption is that 12M is the upper possible limit (18M for non poaching).
And for the focus, that basically mean that in case of litigation, the company would have to prove that:
1. You have market edge knowledge from the company that would result in an immediate and material advantage to the competitors (this one is very hard to prove for the company, and a lot of negociations revolve around debunking this argument)
2. You are going to work on the exact same subject in your new company, it cannot be just based on your field, it has to be very specific to your role in both companies.