Arc'teryx Atom AR

It would work just as well for that, especially thanks to that new super breathable lining fabric that art jokes have used for this season, so that is...

I only use my Atom AR for static activities (such as hanging out at camp). Even my Atom LT is way overkill as a mid layer for anything other than low output activities (such as resort skiing). As the old adage goes, “be bold start cold”. You might have better luck with a micro grid fleece as a mid layer.

I would personally recommend a Koda/Kappa instead for a general use winter jacket. It's a bit warmer and more protective. I love my Atom AR but I don't find it as warm as others here do (as a standalone, under a shell it's a furnace), without exertion I need something heavier when it's below 30F.

And surely in Swedish winters, that moisture will cycle between freezing and melting with your movement and subsequently affect the down (and warmth) in the Thorium (or Cerium). If you're looking for a good active layer, I would recommend the Atom AR. I usually wear a long sleeve base layer + Rho AR fleece + Atom AR + Beta SL and I've found that it keeps me warm enough down to -20C.

I absolutely love my thorium for just general walking around and being static. It is quite warm and works perfectly for this use case. However, I wouldn’t wear it during more intense activities, unless it is very very cold, it is just too hot and I’d worry about soaking through the down. I would go with the atom AR if that was the case.