I personally like top down bottom up cellular shades. They are very insulating and can give you additional privacy if necessary. They come in lots of colors, translucency and textures and are super easy to install. You may want to post your inquiry on the design forum.

They do make shads for half rounds, but that wouldn't fit properly in this case. You are going to need to do something a bit "custom" in nature and I would do it out of the same materials that the blinds will be done in (assuming fabric vs. wood).

I think you are on the right track with a crisp white roman shade. But go a step further and take advantage of some of the nice other colors in your room like the blues in your rug or the magenta desk top suede. Use a color border in your roman shade. Here is an example...

Seems to be a decent distance across the lake. Problem I see is that even though you think you won't splash stuff up to the top...you will. Happens all the time. Like wearing a white shirt to a picnic. Not a question of if, but when. Backlighting on the window does effectively reduces the reflectivity of the Low-e and make what is inside, more visible. You could turn on a bit of under deck lighting and that would help hide what is inside by the reflectivity.