Since the tops of the windows seem to be at the same top height, I would go with the shorter wall height for both window walls. Since you have so many windows close together, I really think all curtains should be hung at the same height or it might look “unbalanced”?

Agree with above ^

Yes make them evenly hung with the shorter walls ceiling.

Thanks everyone!

One would never hang them leaving the gap the taller ceiling height gives. That would look so silly. Hang them at the window trim.