Portage salarial and I.T. contracting in France?

I’m a freelance I.T. contractor, have been using an umbrella solution in Ireland for the last three years, and have recently been offered a 12 month contract to work in France. A combination of the recruitment agency and another third party involved mean that I can’t register my existing umbrella solution for use with this contract and am therefore looking at the alternatives. So far, it has been suggested that I have these options:

Portage salarial via a sister company of the agency. This appears to be similar, if not identical, to umbrella arrangements elsewhere in that, for a management fee, the agency handle invoicing and deductions and provide me with a payslip and net pay. Traditional freelance, which would allow me to benefit from a greater net pay (~60% of invoice value?) by avoiding the mgt fees charged by the agency in 1. but with the overhead of handling invoicing, processing payroll etc. Auto-entrepreneur - this seems to offer a similar solution to 2, except that I can benefit from a higher net pay up to 34,000 euros.

Please could you comment on the accuracy of the summary above? Assuming it is broadly accurate, I’ve decided to explore 3. So far, I’ve looked into acquiring a French address in order to register as auto-entrepreneur. However, I’m unsure whether, as an I.T. consultant, I’m eligible to use this route.