Thank you both for your comments.
@dgobbi David, you were right pointing out the issue about the scale factor. Indeed the scale was set to 125%. I set the scale to 100% and voilà I got a resolution of 1920x 1080 which appears the maximum my laptop can achieve (it is new laptop just bought it last month).
However, I am still interested in this question as the resolution affects the analysis I am interested in conducting. It would appear, following @Paulo_Carvalho that using Qt it might be possible to achieve larger resolutions. Is setting VTK with Qt hard to achieve? Can this be done using Python?
Thanks again both of you for your help and interest!!!