When I create a new project, there is no choice between iPhone 12 (mine) and iPhone 16 (daughter’s)
Is this a conscious action or a small omission:) ?
You can set the Design Screen to whatever height and width your want. Have a look at Form Properties designHeight and designWIdth.
There is a defaultFormSize in Project Properties which you can also set. Of course, at run time, it depends on how big the device is. A well designed app will dynamically adjust its appearance depending on where it is running. This is called Responsive Design.