VirtualBox Guest Additions confusion - vboxsf OR vboxvideo - not both

I'm having some issues understanding what is happening on a Slackware64-current guest (RC1 5.14.2). VBox version is 6.1.26. There are a number of threads in this forum that are somewhat related to guest additions not working and I can't seem to find a definitive answer.

Problem and TL;DR: Installing VBox Linux guest additions will correctly load the vboxguest and vboxvideo drivers, but not the vboxsf driver (see below). Removal of the guest additions allows me to use the kernel vboxsf, but not the vboxvideo driver.

Code:# lsmod | grep vbox
vboxvideo 32768 0
drm_vram_helper 20480 1 vboxvideo
drm_ttm_helper 16384 2 drm_vram_helper,vboxvideo
drm_kms_helper 294912 3 vmwgfx,drm_vram_helper,vboxvideo
drm 626688 10
vmwgfx,drm_kms_helper,drm_vram_helper,vboxvideo,drm_ttm_helper,ttm
vboxguest 385024 5

# modprobe vboxsf
modprobe: ERROR: could not insert 'vboxsf': Unknown symbol in module, or
unknown parameter (see dmesg)dmesg give this:
Code:[ 638.204519] vboxsf: Unknown symbol vbg_warn (err -2)
[ 638.204555] vboxsf: Unknown symbol vbg_get_gdev (err -2)
[ 638.204600] vboxsf: Unknown symbol vbg_hgcm_connect (err -2)
[ 638.204635] vboxsf: Unknown symbol vbg_hgcm_disconnect (err -2)
[ 638.204656] vboxsf: Unknown symbol vbg_err (err -2)
[ 638.204663] vboxsf: Unknown symbol vbg_status_code_to_errno (err -2)
[ 638.204671] vboxsf: Unknown symbol vbg_put_gdev (err -2)
[ 638.204686] vboxsf: Unknown symbol vbg_hgcm_call (err -2)I know there are drivers included in the kernel now, so I tried to uninstall the vbox guest additions and use the kernel drivers.

Code:# ./VBoxLinuxAdditions.run uninstall
Verifying archive integrity... All good.
Uncompressing VirtualBox 6.1.26 Guest Additions for Linux........
VirtualBox Guest Additions installer
Removing installed version 6.1.26 of VirtualBox Guest Additions...
vboxadd-service.sh: Stopping VirtualBox Guest Addition service.Reboot and check for loaded drivers. The only one listed now is vboxguest. So I modprobe the vboxsf driver and now it works as expected - but there's no automouting. I'll have to add vboxsf to start at boot and then add the mount command to fstab or rc.local perhaps.

Code:# lsmod | grep vbox
vboxguest 45056 0

# modprobe vboxsf
(no errors)
# mount -t vboxsf share /media/share
(sucess and files are visible)But now the VM is at a fixed resolution and if I modprobe the vboxvideo driver, it loads without error , but it has no effect on my ability to resize the screen. So I've fixed the vbox share issue, but now I have a video issue (and without the driver the VM is/appears horribly slow as well).
Code:# modprobe vboxvideo
# lsmod | grep vbox
vboxvideo 32768 0
drm_vram_helper 20480 1 vboxvideo
drm_ttm_helper 16384 2 drm_vram_helper,vboxvideo
vboxsf 45056 1
drm_kms_helper 294912 3 vmwgfx,drm_vram_helper,vboxvideo
drm 626688 10
vmwgfx,drm_kms_helper,drm_vram_helper,vboxvideo,drm_ttm_helper,ttm
vboxguest 45056 1 vboxsfI've also tried to install the virtualbox-kernel-addons 5.2.8 from Ponce's SlackBuild repo, but it fails (after a couple of hours) with a message that simply tells me it cannot find vboxvideo.ko. I'm not sure how the versioning for the SBo package is - I can't find "kernel-addons" on the VBox site to check for a newer/compatible version. Until now I've never used the SBo packages - just the .run file from oracle along with the guest additions virtual ISO. So I might be doing this completely wrong.

virtualbox-kernel-addons.SlackBuild failure:

Code: ld -r -m elf_x86_64 --build-id=sha1 -T scripts/module.lds -o sound/usb/usx2y/snd-usb-usx2y.ko sound/usb/usx2y/snd-usb-usx2y.o sound/usb/usx2y/snd-usb-usx2y.mod.o; true
ld -r -m elf_x86_64 --build-id=sha1 -T scripts/module.lds -o sound/virtio/virtio_snd.ko sound/virtio/virtio_snd.o sound/virtio/virtio_snd.mod.o; true
ld -r -m elf_x86_64 --build-id=sha1 -T scripts/module.lds -o sound/x86/snd-hdmi-lpe-audio.ko sound/x86/snd-hdmi-lpe-audio.o sound/x86/snd-hdmi-lpe-audio.mod.o; true
ld -r -m elf_x86_64 --build-id=sha1 -T scripts/module.lds -o virt/lib/irqbypass.ko virt/lib/irqbypass.o virt/lib/irqbypass.mod.o; true
make[1]: Leaving directory '/usr/src/linux-5.14.2'
install: cannot stat 'vboxvideo.ko': No such file or directoryThis VM is a fresh full install of current - the virtualbox tools are the only thing installed.

Any ideas or pointers would be helpful and most appreciated.