The only problem I see with just one drape on each window is that it's going to be swooped across a fair amount of the window blocking part of your light. Regular panel curtains could be opened and let in the maximum amount of light.

I was going to put a rod over the arch and have two panels on each window. Open all the time essentially.

I would like straight panels on either side of the window, at the top of the arch, but I would never plan on closing them unless you need to for privacy. I wouldn't do a sheer however; I would like a solid, or a little print that reads as a solid from a distance.
I do see that you have a cathedral ceiling. If you're not in love with the arches on the windows, a dramatic look might be to have roman shades coming down from the (slanted) ceiling line, and just cover the arched area! It would help fill in what looks like a big wall area.

I think that would soften up the look of the room, and add color and personality as well. Should look nice.