can a Xen/KVM VPS Node server support overselling/overcommitting of the RAM/CPU? Is there any information about this topic?

I found KVM supports it, but no details on how to achieve that:

except Virtualizor way ($1 to $9 monthly, ipv6 support)

Small update: Here is described KVM overcommitting resources like RAM, CPU: http://serverascode.com/2013/02/20/overcommitting-with-kvm.html
http://www.linux-kvm.org/page/KSM <- KSM = Kernel Samepage Merging

Here is mentioned "KVM memory ballooning": http://www.linux-kvm.org/page/Projects/auto-ballooning
How to use virtio: http://www.linux-kvm.org/page/Virtio
"How to use Virtio: Get kvm version >= 60; Get Linux kernel with virtio drivers for the guest; Get Kernel >= 2.6.25 and activate ;
CONFIG_VIRTIO_PCI=y (Virtualization -> PCI driver for virtio devices)
CONFIG_VIRTIO_BALLOON=y (Virtualization -> Virtio balloon driver)
Another overview of the way to overcommit RAM on KVM: https://avikivity.blogspot.ro/2008/04/memory-overcommit-with-kvm.html (10 years old article)