Thank you. This essentially solves the aspect ratio problem. Basically inspired by your suggestion, I found that I can just get and set the aspect ratio using getAspectRatio() and setAspectRatio() respectively.
While appreciating your answer, I must unfortunately emphasize that this is the least of the problems I describe in my original post. Still, in order to get a full screen in this way, I would have to automatically maximize the window at the beginning, and I have no idea how to do it. Apparently I found a thread on this forum discussing this problem, but it doesn’t seem to provide a definite solution - at least not for macOS: