Our window manufacturer gives us the choice of whether we want to have the patio doors or floor-to-ceiling windows (with forend) with or without a flat sill.
These have only 2cm height and cost per window element 80 dollars more. What bothers me, however, is his comment: "It is worth mentioning that with a forend design in the area where the two sashes meet in driving rain and wind on the window, it can happen that some water is pressed into the room.
In this design, there are virtually two side-by-side patio doors, of which previously always provided only one of the two wings."
I don't understand the last sentence, but water in the room would be dumb? What are your comments on this?
Does your neighbor's balcony happen to be above your patio? Either way, I would do it this way with a faceplate and flat sill.
We have "flat sills", so far a very good decision. So far, no water has entered the interior. Being cautious people, we installed drainage channels on the outside (found unnecessary by the civil engineer, but the authors of the relevant standards are into it).