No, VBox does not use KVM unless you use some off brand backend, which is an extra layer of complexity and software you must install and manage.
Absolutely everything you might want to do with VBoxManager is going to be available via virsh and the multiple libviet utilities.
I’ve never had a reason to look elsewhere.
Not using Type 2 hypervisor would be a good one. Not being beholden to Oracle’s shitry licensing schemes is certainly another.