To see what driver is in use you can simply open a terminal and type
it should show you something similar to that
glxinfo | grep NVIDIA
as output, in the version string you see the driver version.
server glx vendor string: NVIDIA Corporation
client glx vendor string: NVIDIA Corporation
OpenGL vendor string: NVIDIA Corporation
OpenGL version string: 3.3.0 NVIDIA 270.41.06
KDE in 11.4 is 4.6.0.
You can check that by
in the terminal, which shows something like
For your resolution problem, I think it is somehow related to your monitor, I hope someone else has an idea about this. It is too long ago I used CRTs.