yes the vboxservice is just loading some important modules at boot time. In artix I installed virtualbox-guest-utils and installed a service to /lib/systemd/system. One can translate this systemd stuff to openrc by making a script in /etc/init.d and loding modules from /etc/modules-load.d/. Unfortunately it’s still not working. This is what every “I hate soystemd” person was telling for years and now I realize why he/she is are correct. You cannot get the virtual box guest auto resize in a non-systemd distro. I have tried hundred of ways but it isn’t possible. Not with runit not with openrc. This really sucks. Get ready for a systemd kernel. Hours of research to know why systemd sucks 
I will still try if virt-manager helps or not but as for virtualbox it doesn’t work in non-systemd.
I will still try if virt-manager helps or not but as for virtualbox it doesn’t work in non-systemd.