I think they'd look better fuller (I think the height is fine), but if you add additional panels you'll lose a bit more of the view when the drapes are fully stacked open. I'd be tempted to add a panel to each side just to see how it looks though. (I really don't think what you have now is bad at all.)

Adding a link with photos, so people can see the Hunter Douglas Pirouette. https://www.hunterdouglas.com/window-treatments/sheers-shadings/pirouette

My style is difficult to describe so I've included photos that inspire me.

Since you have the cranks on the windows and need access to them, I wouldn't put anything there. Valances can be old fashioned and your windows are more contemporary. If I didn't need privacy, I would forego window treatments. The views are nice, but if you don't want to see the deck and its furnishings, try an inside mounted semi-sheer cafe curtain on the tall window. That still allows a view of the trees, but will block the deck and railings from sight. Add color to the kitchen with some colorful hand towels, pot holders, crocks/cookie jars/canisters, a kettle or small appliance. If you limit the items to a few decorative accessories, you can change them out when you feel the mood or the seasons change. Pops of orange A bit of lemon Turquoise