Is type-2 hypervisor more safe than type-1 hypervisor?
No, it’s the opposite. Type-1 hypervisors run directly on the hardware without the need for an underlying operating system, thereby reducing the attack surface. This results in increased security and more efficient utilization of resources (security through design).
When it comes to exploiting the GPU, whether through 3D Acceleration in VBox or virtio-gpu in KVM, these are recognized security vulnerabilities holes that Whonix cannot address. However, Whonix does not use or enable these features by default.
More read: Why Use KVM Over VirtualBox?
Or its all over the internet why KVM (hypervisor type-1) more secure than VirtualBox (hypervisor type-2).