@caminowilts, as mspath - our winter-walking guru said, there is a recent post with lots of info.
Regarding your pack - depends how minimalist you are!!!! I walk with an Osprey Kestral 38. My sleeping bag weighs just under 1kg and measured approx 21cm/19 cm packed in its bag. It fit in the bottom section of my pack. I had a large microfibre towel that folded up palm size, I carried a short and long merino shirt, thick hiking pants, wet weather pants, toiletries, a lunch bag full of 8 weeks work of medicine, 4 headlamps (family of 4 walking,), a few other items. Despite the minimal amount stated above, cant say I packed ultralight. My pack was full but not overflowing, it weighed approx 7.5kg.
First camino with a water bladder (similar to camelback), second with water bottle.
This is my sleeping bag - was toasty warm each night - sometimes a bit too warm!!!
If walking in winter, I would recommend ear warmers (headband style), a buff, beanie and very warm gloves. My husband and kids didn't bother with a beanie, they fashioned their buff into a hat, then one son wanted to wear my beanie all the time haha.