With the VESA VBE driver, nothing is offloaded to the GPU for acceleration.. it's just a dumb framebuffer, so rendering graphics will eat up your CPU time.
Driver development is a commendable goal, but unfortunately nVidia does not release documentation for their graphics hardware.. available drivers are reverse engineered, obfuscated, or proprietary.
Just a small note, the detection of an nVidia
azalia(4) device is common these days, but unsupported, this is for using audio over HDMI cables, apparently it's being worked on though.