However you hang it, keep in mind that once the sheer fabric falls in front of the back fabric, the sheer will change color. So, let’s say you have pulled back the thermals, but not the sheers. Where the sheers hang over the stacked back thermals will not be the same color as the rest of the window. It doesn’t sound like a big deal until you see it. It is very obvious.

I assume the windows abut in the corner? This would make it tricky to have romans as they would probably clash when both drawn up. Curtains drawing away from the corners add softness to a dining area, but make them floor length as short curtains look a bit half mast. It is also a good idea to have them wider than the windows to allow more light in when opened and fitted from above the window to elongate the window.

You are correct the place does and always will look a bit sparse when you only have blinds. The question with curtains is sometimes dependant on what climate you live in and I am not sure where you are so I am going to say. If you need curtains for heat go for a quality curtain to the floor with a fabric that is not stiff (as I discovered I now own after buying curtains off line for my spare rooms). The expensive curtains I brought for my living room have a softer texture and hang so much nicer. As I need Curtains / Roman blinds for heat I have backing fabric etc on the expensive made to measure ones, where as the cheaper ones are just thermals. If you only want to add a curtain for looks and do not require it for heat I would recommend going with a lovely sheer / half see through fabric that drapes really well, this will add a point of interest and you can colour match or add a loved colour to a bare - white on white - cream on cream - colour scheme.

Wow - what a view! Yes definitely take the curtains to the ceiling it will add grandeur and frame the view even more beautifully. You can get a custom bent track made that will take the curtains around the corner so the window is not obscured when the curtain are open. Contact your local interior designer - they'll know what to do