Down jackets advice please

I am moving to Tajikistan for work for a couple of years. I am keen to be out in the mountains hiking, camping etc - winters are cold with temperatures of -10Celcius in the capital (at 800m elevation)and a good deal colder higher up (there are limited reliable data available). I hope to be able to be out walking and camping in fall and spring, but perhaps only day walking in winter. I want a down jacket that will be warm and also that will pack up reasonably small and light. I also wish to be able to use the jacket in town on winter days.
I'm reasonably experienced in mountains in Europe and South America and have a good goretex shell and a range of different fleeces, base layers etc. Please could you share some recommendations with me on down jackets. I have read reviews of the most commonly available makes and am left wondering:
- is a jacket or parka best - as i understand it, the main difference is in length?
- what about the outer coating of the down jackets? Some offer some level of water resistance - how effective is that? Are there good and light down jackets that could be worn without having to worry about a goretex shell over the top in wetter weather?
- I currently live in Lima, Peru where there are TNF Nupste, Mountain HW Sub Zero and Lowe Alpine Down shield jackets available - but could purchase online from the US/Europe.
Many thanks
Andy