We will have 5 days in Barcelona. Need to end up in Normandy in France and have about 4 days to do this after leaving Barcelona. Considering staying on Spanish side to San Sebastian, but should we head for Bordeaux instead? Also not clear yet whether a Eurail pass makes sense or buying tix directly. Can we use the pass to stop off in a town for a night or two, then board another train? We want to avoid a car rental, just use the trains. Is this realistic? I love the look of the small towns on the coast, like St. Jean de Luz. Thanks for any advice!
You will benefit from studying this encyclopedia for rail travel: www.seat61.com
Many posts, here and elsewhere, contradict the assumption that a pass is a good deal. There is a variety of passes (see Seat 61.) The only way to know which if any could save you money is to first sketch out your route and find the point-to-point prices, often through using the appropriate national train operators' own sites. Again, check out Seat 61.
Many, not all, long inter-city trains require a seat reservation, included in the point-to-point ticket but passholders must purchase it separately. And most major routes are not hop-on-hop-off. The seat is assigned for a specific day. The next train is a separate ticket so you may need a separate reservation. To wander at leisure, search for local/regional trains. It's easier to find them if the search engine function "direct trains only" is switched off.
val,
Where are you planning to stay in Normandy? One of the quickest routes by train will be to use one of the direct (no changes) high speed train departures from Barcelona Sants to Paris Gare de Lyon. The earliest one appears to be at 09:20, arriving at 15:53 (time 6H:33M, reservations compulsory). The trains travel at up to 300 km/h so it's a very quick trip!
From Gare de Lyon, you could use the Metro (Line 14) to Gare Saint-Lazare which should take about 10 minutes. You could also use a Taxi but that will be subject to traffic and I'm not sure whether that will be a problem at that time of the afternoon.
You'll be able to get to wherever you're going in Normandy from Gare Saint-Lazare, but it's impossible to offer more specific directions without knowing where you're going there.
The route you wish to take via San Sebastian will see you spend quite a few more hours riding the rails than if you went via Avignon, Lyon and Paris.
San Sebastian is difficult by train from Barcelona. Your best bet is to get the direct early morning Alvia service to Bilbao, arriving in time for you to check out the Guggenheim. Take a local train or bus to San Sebastian the following day.
There is a change of rail gauge at the Spain-France border so you won't find a direct train from San Sebastian to Bordeaux. Your best bet is to use local transport to get to Hendaye for a direct TGV service to Bordeaux.
Then another TGV to Paris from Bordeaux, with a change of stations in Paris from Montparnasse to St Lazare for trains to Normandy.
As you can see, quite a lot in 4 days. And yes, you will need to buy separate tickets for each premium (Alvia/TGV) train.
If you are going to go to the trouble of reaching the Basque Country, you should spend more time there, visiting different places before heading on up to Bordeaux. People don't realize how much of an outlier the Basque Country is and how difficult it is to reach. According to rome2rio.com, the train from Barcelona to San Sebastian is almost 6 hours. On the other hand, it's a 30 minute regional train ride from San Sebastian to Hendaye on the French side of the border, and then 2.30 hours by TGV to Bordeaux. From Bordeaux, you have to do as said previously, TGV to Paris, change stations, and train to wherever in Normandy. (Or according to rome2rio, there is a train through Tours-Caen twice a week, avoiding changing in Paris.)
Therefore, once one the Atlantic side of Spain, I'd spend as much time there as possible.