I am a cold sleeper so would take the -10 C sleeping bag. I suspect the heat will get turned down, if not off at night in some albergues. It is easy to cool down if your sleeping bag is too warm. Take off last layers of clothes, sleep with bag unzipped. Getting warm in a cold sleeping bag is a little more difficult... I've put a metal water bottle filled with boiling water in a heavy wool sock, and given it to a pilgrim that was cold to warm up her sleeping bag. If you have dry long johns, you can sleep in them, but I find my layers of clothes are damp with sweat, whatever the weather and I need to hang them to air dry over night.
As for the need of a "winter" jacket, (By that, I assume you mean an insulated jacket)
I would plan on layering my clothing, depending on the conditions.
-Base layer of polypropelene or merino wool.
-Mid Layer of merino wool.
-Outer layer, synthetic fleece. Wind Stopper fabric if possible.
-Overcoat - Waterproof shell and matching pants.
I guess an insulated coat could be used instead of an Outer Layer and Overcoat, but I'd like the option of wearing just the outer layer, or the overcoat, depending on the weather conditions.
You will figure it all out.
buen Camino,
David, Victoria, Canada