Freelancing for a UK company - auto-entrepreneur or portage salarial?

I am moving to France in May and will be working on a freelance basis for a UK company in London as a digital marketer. I’ve done a fair amount of research regarding tax and business structures and was hoping to get some further advice as I’d like to know the most tax-efficient way to claim my income. Here’s my situation: Working from home in France, travelling back to the UK once a month for meetings, earning roughly 35,000 euros/year. I’m aware that having just 1 client could lead to issues if I set up a business, so bearing that in mind, here’s what I think my options are. Register self-employed/set up a business. In the three scenarios below I would have the UK company as my main client to begin with, and then plan to find a second client before the end of the financial year.

1. Auto-entrepreneur: Invoice less than 32,600 euros in total for both clients, paying the lower rate of tax and social charges.
2. EI: Invoice my normal charges (35,000 euros), pay tax based on regime reel.
3. EURL: Invoice my normal charges (35,000 euros), pay the fees for setting up a limited company, pay social security on income withdrawn and then corporation tax and tax on dividends.
4. Work through Portage Salarial: Just work for the one UK company, paying normal social charges, income tax plus the fee of the portage salarial.

Which of the above four options do you think would be most tax efficient, considering I only just miss the 32,600 euro threshold for auto-entrepreneurs? Even though setting up as an auto-entrepreneur would involve taking a pay cut, I think I would actually take home more due to the lower tax/social security rate. Also, I’ve heard that as an auto-entrepreneur you can’t invoice more than 75% of your charges to one client, is this true? Is there a way of paying normal employee income tax/social security without going through a portage salarial?