Since you have 10% on the other room, you will notice a "big" difference on the look and how much light blocks on one x the other. Indeed, the 3% will block ALOT of light during breakfast.
In regards to the controls, I am sorry about your troubles, but I would NEVER recommend spring loaded over chain. With chain (cont loop) you would have a much more precise controlling of the shade.
One fact that not many people know if the color:
even with the same openness, a darker color will allow more view to the outside. On the other hand, a lighter color will maintain the room cooler. See photos attached.
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Mona roman shades
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