KERNEL-virtualbox-guest-module contains only vboxsf lib.
The rest is kernel supported.
And no - VMSVGA do not work as well as setting the VBoxSVGA before launching the installer. And you are right - it is the graphics driver which is the culprit - and the best result comes from selecting the correct device before installing.
Believe me - I speak of experience - if you do not use VBoxSVGA your screen resolution needs to be set manually using the given editions settings manager or using xrandr. And it will cause you a great deal of grief.
The issue was driving me crazy during finalizing the last ISO and I was strongly compelled to include the advise.
So there is no need for KERNEL-headers and dkms.
If you need the extra goodies then install the Oracle extension pack.
pamac build virtualbox-ext-oracle