What is your window height with high ceilings?
I don't know, but maybe there is such a standard?
If you want to install roller shutters/blinds, add another ~20-25 cm and another ~20 cm for the lintel. That means the lintel would have to be 2.3m high. Then I would plan for 1.4m high windows with a 90cm parapet. Without the louvers, I would even plan for 1.6m.
With 2.72m ceilings we have 1.51m windows with 92cm parapet height , with 2.42m floor to ceiling height windows.
And no blinds on the window sills, but with Venetian blinds on the floor-to-ceiling windows.
With a ceiling height of 2.70 m, I would recommend a window height of 1.385 m, and for floor-to-ceiling window elements of 2.26 m. At this height, there is enough room to install top-mounted roller shutters, and they are pleasing to the eye as they match the height of the room.
If you want to install roller blinds, you need approximately 30 cm.