$ pacman -Qs virtualbox
Powerful x86 virtualization for enterprise as well as home use
Oracle VM VirtualBox Extension Pack
The official VirtualBox Guest Additions ISO image
VirtualBox Host kernel modules sources
The id at host should include group vboxusers for the user that starts virtual machines. Why do you use root at the host?
Remove the virtualbox-guest-modules and virtualbox-guest-utils from the host.
Note that virtualbox-guest-iso is optional and needed only for VMs that don’t have guest additions already, like Windows.