How about inviting a mobile service to your home to get you started in deciding what you like - alternately take some samples home from a store. There are good online blind companies that will save a lot and will send you samples. You can also ask your local fabric stores which fabric lines they stock - You can then look online at your leisure and select some favourites. Go back inshore this will help the consultant know what you like.

We have done a lot just like that. Typically we put a sheer on a track over the window / door and a plain thermal roller blind inside the frame (behind the curtain) The the same roller blind is put in the kitchen. This gives you the ability us the roller behind the curtain as a lining for night or cold days and creates flow between the kitchen and dining space. A thermal roller is very practical in a kitchen as they are cleanable and roll up out of the way when not in use. Here's a dining room that I did. In this case we used two different fabrics and both are in the dining room / kitchen. (in this example its not over a working kitchen space but it would work just the same) This photo shows how the linen drape and rollers mix over a door and a separate roller blind looks next to it. Its super functional, cost effective and right on trend. In your case I would keep both the roller fabrics the same. Hope this is of help :)

Please don't install verticals. You have such a beautiful home, I strongly believe drapes will look amazing. With curtains you want to install them as high as possible, I would install on the same level as your kitchen cabinetry, so about 10cm below the ceiling cornice. Colour, I recommend two shades darker or lighter to give the room dimension. I feel a classic look will last you a lifetime so a plain coloured drape, and if I were you I would add a border in another neutral colour to further add interest. I will show you a photo of a drape I did for a client and I think this style would suit you. She chose Madison Linen fabric with a dark grey border.

Yes, the steps are a small challenge. My suggestion is to work with that angle of the steps. If you would like full block out curtains, angle the hem of the curtains with the steps. With the width of the opening, and having the curtains pull to each side from the middle, there will be quite a bit of bunching. So I would suggest one curtain fitted across left hand window. Then the remainder of curtains pull from the door opening panel, back to the right. Depending on our much 'block out ' you require, I think the following product from luxaflex looks your style, but would not bunch up on the sides as much as traditional curtains. https://www.luxaflex.com.au/products/blinds/lumishade/ Still working with the angle on the steps.