While on CF the routine is sandwich of ensalada mixta for lunch, pilgrim dinner at night. None of that on CdN: there is real and delicious food available! Food the locals actually eat.
Take a snack with you if you want to eat something around noon, but I would suggest to eat later in the afternoon, once you arrive at the albergue, around 2-3pm. Go to the local restaurant and order the Menu del dia. For 10 euros or so it will be soooo much better than any pilgrim menu you have ever had. And it's important to make that meal your main one because at night you will find very little being offered before you head to be: mostly sandwiches, especially is smaller towns.
In larger towns you will find Pinxos in lovely bars, and I would encourage you to enjoy them. Lots of very well known places for pinxos in San Sebastian and Bilbao. Depending on the area you are in you will find local delicacies, or not so delicate but delicious such at the fabada or cocido asturiano. A heavy soup with beans, chorizo, blood sausage. Delicious. Also lots of fish, usually fried. Try the sardinas. In Santona stop and have some anchovies. In Bilbao croquetas.
Ate a a wonderful place in Santillana del Mar called El passaje de los nobles, it's on the main pedestrian street as you walk up to the Colegiata. Menu: fabada, cocido montanes, ensalada de queso de cabra, bacalao con tomate natural, brocheta de solomillo iberico at vino tinto, and for dessert the best lemon mousse ever.
In Llanes enjoy the Carbayones, local patisserie and eat at the Covadonga, 11 euros menu day and night. People queue at lunch time, so get there a bit earlier.
There's a lovely family owned restaurant in Hazas/Liendo, mother cooks. It's not the one on the main square but may 50 meters from it in a stand alone house in the middle of a carrefour. Grilled red pepper stuffed with bacalao! And in San Vicente, in the row of touristy shops and restaurants, there's one that stands out with its menu. I can't remember the name but it has blue and white tiles going around the main entrance. Had grilled sardines there.
I strongly suggest you start learning the words for the different types of seafood: carbacho, gambas, bacalao, chipirones, merluza, bonito, etc. Also cuts of meant: codillo, etc.
Breakfast will be the same as on the CF: croissants, toast or if you are luck tortilla de patatas.
Boy that just made me hungry! Hope this answers some of your questions!