Proportions: 19:10 is almost twice as wide as it is high, 19:8 almost two and a half times as wide as it is high.
Opening sashes should not have (significantly) more width than height, otherwise they will often need readjustment.
As the only window in the children's room, the window will be large enough to illuminate it - for a 12 sqm children's room already the smaller one, for a 20 sqm children's room also the larger one just barely. But what is 1m window height supposed to be for anyway: should the child in the first school year have to climb onto the table to look outside – or crouch down in the last school year?
Google Le Corbusier Modulor.
In case it wasn't clear enough from the contributions of the other discussants: a 1m flat viewing slit is just enough at the top or bottom.
And 2.385 m width is useful for a fixed element (in the kitchen as natural light for cutting onions) but with opening sashes it would have to be two- or three-leaf.
The mentioned width at both heights is not a window in the practical sense, but a stylish lookout for the function-follows-form faction.
And such hyper-wide horizontal arrow slits definitely do not go with vanilla-colored bricks and a half-hipped roof!
but if XY tells me that the planned 2.80 x 1.00 window is simply too small/dark in the children's room and with him sh....
We have such windows in both children's rooms – Horst-Kevin prefers playing in the treehouse, and Lisa-Chantalle definitely wants the exact same one in her dollhouse