Clothes - yes, light is good, warm is better. I'm a Merino convert. Two t-shirts, (150 weight) , one long, (200 weight). Can't tell any difference between the 100%merino and the 80%., less I find uncomfortable, and gets smelly faster. 1 light weight puffer, previously mentioned. Rainwear. It will rain, the only question is how much.
I'm a bloke, so evenings long zip off pants for me. Second pair or shorts for the day.
3 pairs socks and underwear, because you simply can't guarantee you'll get things dry. ( Obviously I'm talking total - 1 to wear, 2 spair). Beanie etc
Food - I'm talking lunch. I've always got dried fruit and salted nuts with me, often a little chocolate. Or a Snickers bar. Sometimes a few biscuits/ crackers. I'd normally pack a banana and,/ or apple or similar. I can survive just on that, a sandwich of some description is a definite bonus.
The only days where taking it with was important were, for me, day one ( as mentioned, everything shut,) and the Hospitales. (4 of us shared a baguette, some chippies , a large tomato and a large (250gm?) tin of tuna, we all had our own fruit etc and at least 2l water).
But I started every day with breakfast, even if it was just a yoghurt ( or a long life yoghurt Drink, popular here) and a few breadsticks. And coffee, of course! I'd rather start late than miss that. A couple of times I could pick that up an hour or so in, but not always. Many of the little towns have zero services. You don't need to go crazy, but 2 - 300 grams food can make the difference between a really tough day and a great one.!