Cool Weather

My suggestion is to wait until the trip is close to finalize packing, using the ten day forecast (the closest that is reliable). The weather is out of whack, so "typical" temps may not matter. I was in Switzerland last October and it was the warmest October on record. I was wearing short sleeves after worrying so much about cold.
As to what to take if it actually is cool and rainy (it's the wet that gets to me), I packed wool "base layers"--don't think that means thick and scratchy. You can get thin and soft wool leggings and tops that wick sweat away while keeping you warm. They are easy to roll up for packing. I'd plan on the rain parka with the lining again, in all likelihood. I take wool socks too, even though they are bulky, as there is nothing worse than cold feet!

Actually my experience with puffy vests is that they compress a lot. I’m traveling right now and put my waterproof rain jacket with a hood, a puffy vest (32 degree brand from Costco) and rain pants into a compression packing cube. It squashed down a lot although the package weighs 3#!! I use older Eagle Creek compression packing cubes for the bulky stuff. I do pack light-my bag has to be light enough for me to lift into an overhead bin - was 17# on my way out the door this time.

If you tend to be cold, maybe pack a thermal layer? I’ve also got base layers from 32 Degrees and they are inexpensive and work well for me in winter.

My favorite jacket is down because I can put it in a gallon zip lock, sit on it, seal it and it's about the size and weight as a pair of trousers. But more to the point, I spend a lot of Falls in a place with very similar weather and I bring lightweight nylon long sleeve shirts and cargo pants. Then I wear a set of mid weight long John's if it's colder. Sometimes top, sometimes top and bottom. Really cold, the down jacket comes out.

I have found that I can stay warm down to 40 degrees F with a good fleece jacket and a rain shell. I have a Patagonia better sweater fleece and a Marmot waterproof shell and by layering them over my shirt I'm fine. These are easy to pack and I travel carry on only.

Donald and I have the same approach. Layers. It is really quite incredible how warm a fleece topped by a rain coat can be. It is so much more versatile, too, because each can be worn alone. We did a January trip once, started in warmish Barcelona and then Austria and Switzerland which, of course, was winter. I didn't bring a winter jacket. With a long sleeve shirt (or a long underwear shirt, fleece top or thin sweater, lightweight jacket and a rain coat, I was toasty. Most often, I just did a long sleeve shirt, fleece and raincoat.

There are so many options for fleece pullovers/jackets and they are lightweight and pack small. I like LLBean, Columbia or Eddie Bauer.

You're already on teh right path via layering. Early October don't be surprised if you get rain, evening temps you'll likely want a cover-up of some sort, just depends upon where your location.

Next to skin you can wear a basic shirt or, double-up with an undershirt. A merino wool t-shirt is a very efficient and thin way to maximize your warmth for the least amount of weight.

Mid-layer either a fleece jacket or pull-over is not as expensive as a down-jacket. Not a big coat but, what's called a down sweater, resemble a low-loft full-zip jacket. You can wear it alone or, as a layering item, also highly compressible and lightweight.
Lastly your outer layer, a light packable rain shell or, maybe something more robust, where you can layer everything up and not feel like you're over-dressed.