I have trim on my windows, unlike yours, very simple & modern, , I’ve had flat Roman shades installed on all, not inexpensive, but look good in my home. Some are just lined, others have blackout linings ( in guest rooms ). All of mine were done by an independent store, so no help re brands, etc., sorry.

Btw, your shell collections are very interesting, I really like them, jealous. :)

On this particular stair window, I would go with bamboo blinds - they would work with the shell art you have there. You mentioned other rooms, but no pictures, but you certainly don’t have to have the same window treatments throughout.

My concern about bamboo blinds and Roman shades is that they look nice in design photos but are often askew when I see them in people's homes. I really need something that has easy and reliable operation which is why I was hoping for advice about particular brands/models.
How would it look if I put a Roman shade or bamboo blind on the window trim for "show" and kept the pleated blind underneath for privacy?

I don’t think the layered look is going to function very well. A textured Roman shade satisfy the design element for the landing window. A patterned fabric roman shade for other ares of the house, like bedrooms, may work. At one time -I’m guessing - your beautiful window frames were finished wood, not painted that offered depth and style for that period.

The house is only 10 years old, the trim has always been painted.

IMO if you lve thet over the top trim get a simple roller blind and be done there is IMO no way to add nice window treatments that do not block the window or stick with what you have and think of all the money you saved . I would not ever put wood or bamboo blinds to add to the heavy look of those windows.

What about this from the shade store? Lifetime warranty, made in USA, 25% off sale going on now. We did our house windows with them and took advantage of the sale.

https://www.theshadestore.com/shades/roman-shades/aventura-roman-shades

Every window doesn’t have to be the same. I have always chosen based on functionality needs and room’s decor. Costs will be less with say only upgrading in LR, DR, Master (see first example below). If you like the idea and would like advice in certain rooms, provide pictures.

Regarding certain styles being askew, it’s ones with cords, and these are no longer sold and remote would be a good choice.

Convenient; just open slats. Choice might be based on the room and your budget.

Textured blinds are attractive and there are lots of design and color options. Good choice if you want matching throughout and not at a huge cost.

Your window trim is lovely. You need “inside the trim” ideas. And every window doesn’t have to be the same. Do each room - one at a time - but you can keep the halls and stairway windows similar. Go to professional window treatment places in your area, and browse the internet for this type of treatment. They do NOT have to be bamboo roller ones.

Here are two pretty windows.