I recently read this article about Capacitive Touch Sensing.
I have a couple of questions:

1) I can't tell if the capacitor that is created between GND and copper is the one I drew in the picture:

If I have made a mistake, I ask you to draw it in the right place.

If and only if I drew it correctly:
scrolling the article, it's showed the effect of the finger.
It says: we can assume that this new capacitor created by the finger (let’s call it the finger cap) is in parallel with the existing PCB capacitor.
2) I then tried to draw the "new capacitor" (the blue one):

Am I wrong or do they not seem to be in parallel?

 

There is capacitance (as electric field energy) between button pad, the PCB ground/common and the universe (that includes the finger when near the pad), so yes, they are in parallel for electrical energy. Usually the PCB capacitance is minimized by a variety of techniques to maximize the circuit response to buttons electric field changes due to the finger capacitance.

https://forum.allaboutcircuits.com/...witch-without-touching-it.200339/post-1904885

There is usually a complex AC waveform (and EM field from the sensor pad) used to sample the amount of charge as a voltage. One method, as the finger increases (in parallel ) the total touch circuit capacitance (with a constant current source charging the sensor pad), the voltage decreases.

The peak voltage changes as a hand or finger is near the sensor pad.

Another method is CVD. capacitive voltage divider.
https://ww1.microchip.com/downloads/en/AppNotes/TB3198_CVD_90003198A.pdf