Between Arcachon and Biarritz, it’s nothing but the Landes forest and endless sandy beaches stretching for nearly 150 km.
Here’s a glimpse of the scenery:
https://maps.app.goo.gl/iBpewkkptfYJ5F3F6
If you're up for it, you'll need a car, otherwise, just take the train.
There are direct trains from Bordeaux to Lourdes, as well as the A63 highway, which I take sometimes. You’ll be skirting the French side of the Pyrenees mountains, I’m not sure what the view is like from the train, but if you stay on the highway by car, it’s really not that interesting. You might as well rent a car in Lourdes and use it to day-trip around the area.
Lourdes itself is mostly just a massive Catholic commercial hub. You either love it or you hate it...
"...If we end in Lourdes, where should we fly out to go home?"
The two largest airports in Southwest France are Bordeaux and Toulouse. They offer flights all over France and Europe, as well as a few flights to Montreal, Canada.
The train ride from Lourdes to Toulouse is direct and takes less than two hours.