I have 3 top end down jackets:
kuiu super down pro have used for several yrs and has done the job very well, lite, packs down small,no issues on down loss and is very warm, not an oven but for the weight and a jacket used back in it checks the boxes
Montbell alpine is an oven a $100 bucks cheaper and longer, does not have have treated down you almost feel like your in a sleeping bag..
just cause I just acquired the Grumman black label and would say it is very similar to the kuiu unit..
just like a wall tent with wood heat late season down is very nice when cold

Adding down pants I waddle around and feel like the kid from Christmas story but warm