French rail is built as a star with Paris in the middle, which is why so many itineraries accidentally become a week in one city. TGV and OUIGO trains run from the capital toward Lyon, Marseille, Bordeaux, Strasbourg and the Channel. Once you are on that network, a second city is a morning, not a project. Regional TER trains fill the gaps. Paris itself is dense, expensive, and worth two or three days if the rest of the country is also on the ticket.
French is the language of the administration. English is common in hotels and stations in large cities and fades in a small-town tabac. Sundays still close more of the high street than visitors from northern Europe expect. August empties Paris toward the coast and the south. The country is walkable at the neighbourhood scale; between regions you sit down on a train.
Charles de Gaulle and Orly are not a gentle introduction. The first hour is wayfinding, a queue, and a decision about a taxi, a bus, or a driver you booked before you landed. After that, the useful unit is a region: the Loire, Provence, Brittany, Alsace. Pick one axis from Paris rather than trying to close a circle around the whole hexagon.
