Down gear definitions needed please; IF possible

I don’t think you can make hard-and-fast recommendations – a lot will depend on your layering system, the weather conditions, your personal metabolism, and the nature of your trip.

Personally I prefer multiple lightweight layers rather than focusing on a single heavier item.  Multiple layers are more flexible if you are walking in changeable conditions.

The temperature range 0C to -10C is relatively modest – we’re not talking extreme cold here, so I would only be carrying a lightweight insulated jacket. I wouldn’t generally use it as active insulation, unless perhaps there was extreme wind-chill such as blizzard conditions. It would mainly be used as a belay jacket during rests and around camp.

But I tend to run hot – the need for active insulation seems to very considerably from person to person.

If you might be using the jacket as active insulation under a hard shell, consider synthetic insulation over down. The insulation in lightweight down jackets collapses into a useless mush if it gets at all damp.

It will be for a static only layer, I still run warm to hot when walking or skiing. It’s only when I stop that I cool off rapidly. It would also be used as part of my sleeping system if it got really cold.
My active layer is currently the Macpac Pisa softshell, along with base layers to suit. Goretex Pro jacket if needed. My real problem is finding a static layer sized like the DAS to go over the hard shell. The DAS fits but I want lighter so I can still ski tour with enough of the right gear

I didn’t think giving an answer to this query would be so hard for people.
I was guessing that it would be a simple answer such as UL would be an inch+ of loft on average, LW 2 inch etc.
Or the same answer but in Clo/TOG values