Effects of kernel drivers on video adapter

am long accustomed to handling of video adapters by Linux. But now doing some setup and testing with FreeBSD 12.1 where things go differently. In spite of all my efforts, the system (except for Xorg(1)) makes no reasonable job on video modes: not a single time did «kern.vt.fb.default_mode» in /boot/loader.conf produce the requested picture and vidcontrol -i mode serves empty list. Secondly, the system does not restore my GeForce 8400 GS to usable state after acpiconf -s 3.
tried to replace the «efifb» driver, along the lines of that thread, with loader.conf’s
to no improvement. nvidia.ko (from nvidia-driver-340) loaded and took over the GeForce, but created an unusable garbled picture instead of text console. Nor the driver managed to resume video signal after ACPI suspending, either in (nominally) text consoles or Xorg screen alike. (Note that [re]starting Xorg brings the picture, albeit only for purposes of X. Switching virtual consoles also is sometimes helpful.)

Similar stuff was discussed at Thread framebuffer-question.68827 but nothing positive came of it except for bizarre suggestion to program a video card via BIOS.

A Xorg nVidia driver does good job with modes… does anything but licensing issues preclude kernel drivers to do the same? Is trying to replace «efifb» a right thing (at least for GeForce 8400)? What exactly are effects of «hw.syscons.disable=1» and «kern.vty="vt"» in loader.conf?