Yes, 32-bit is a creation of Windows; it doesn't actually exist (it's not really a "bit depth", it's a "bits per pixel" value -- the difference is explained in the README somewhere, or at least, it used to be).
For the other thing, the README also comes to the rescue:
Q: I've installed the driver, but my Enable 3D Acceleration checkbox is still
greyed out! What did I do wrong?
A: Most distribution-provided configuration applets aren't aware of the NVIDIA
accelerated driver, and consequently won't update themselves when you install
the driver. Your driver, if it has been installed properly, should function