I've not been to Paris. I don't know how long it will take to get through customs etc.
My relax strategy would be to take a train from CDG and enjoy a relaxing dinner in Biarritz or Bayonne or even Bordeaux. SJPP isn't going anywhere. If you can afford the time, that is.
You have to plan on check-in and security at 2G too. EasyCDG site says 40 minutes check-in deadline and 20 minute boarding deadline.
I think your time appreciation is tight. Its possible and worth trying but if your plane is at all late then you likely won't catch the flight to Biarritz (although its worth going for it till you know its gone because they leave late too).
You have to go through passport control when you enter France. I think it is merely passport gets a stamp; you don't get the impertinent quiz that you get at US and Canada customs. The flight from Paris to Biarritz is domestic. You will likely have to claim your bag (but check with your airline if both flights are same service provider) and go through check-in again at 2G.
As the EasyCDG site says ... the one hour minimum between terminals in terminal 2 only applies if your baggage is checked through to your destination. I think they exclude 2G from that estimate too because it is a remote building.
The EasyCDG site says you can walk 2A to 2F (15 minutes) but 2G is remote and so you need to take the shuttle (N2) from 2F to 2G.
Note that my 47 minutes estimate includes full wait times for N1 and N2 shuttles which assumes you just missed the shuttle and have to wait the full period for the next. The minimum works out to 35 minutes ... and assumes you get on the shuttle and it goes.
If you arrive at Biarritz 1615,You should have no trouble catching the train at Bayonne. You do need to look at the chronplus website to find the last bus you can catch that will get you there in time. Bus 14 Airport Anglet to Gare Bayonne.
If you are really late take a taxi from the airport to Gare Biarritz and catch the 1745 train to Bayonne where it arrives 1755 ... giving enough time to catch the 1806 to SJPdP.