Problem when extending monitor (retina display and windows creation)

Hi all,

I am programming an experiment in psychopy and I am using an Macbook-pro (Mojave) with retina display (13’) connected to an ASUS external monitor.

The thing is that I am trying to draw the stimuli in the retina display but when I have the extended monitor connected to the laptop, the window created in the retina display is divided in 4 quadrants and only the top-left quadrant shows the stimuli (the others are completely black). Moreover, the coordinates in the top-quadrant are not correctly centered… If I create a window without the extended monitor, everythings looks reasonable. And if I create the stimuli in the extended monitor, again everything looks good.
Does someone have a hint about what could be going on?

Three more possibly related but easy to answer questions:

1 When I setup the Macbook retina screen in the monitor center, should I define the pixels in physical pixels (2560x1800) or in “virtual” pixels (1280 x 900)? It is not clear to me what is the correct way to configure the screen after reading previous posts.

2 Does presenting the stimuli in a window or fullscreen has an impact on the frame rate precision?

3 In builder you can choose window type: Pygame or Pyglet. What is the difference between both types of windows?

Sorry for my ignorance, I am pretty new in Python :S
Thank you for your help,