I agree with the general advice to give yourself more time to get from the airport to the train station in Bordeaux. I used this airport 2 months ago travelling to Irun/Camino del Norte.
Note that statistically, budget airline flights that arrive before noon tend to be more or less on time, those that arrive in the afternoon tend to arrive late, and those that arrive in the evening can sometimes arrive super late (because each plane makes on average 6 flights per day and the delay increases with each flight)
For example, the Easyjet flight from London Gatwick yesterday (Saturday) was scheduled to arrive in Bordeaux at 14:15, but arrived 40 minutes late (
see link) and landed (touchdown time) at 14:55 meaning the passengers probably left the terminal at 15:20-15:30 and getting on a 16:00 train from the station 15 km away could be quite difficult.
I also hope you don't fly with Ryanair, because they are currently leaving Bordeaux and started cancelling 40 different routes to and from there. By October they may not be flying there at all.
Ryanair will close a base in Bordeaux—one of four it operates in France—at the end of the summer 2024 season.