Virtual Box is a Type 2 hypervisor, which means it’s running on top of the OS, and not directly on the hardware.
KVM is a Type 1, which runs directly on the hardware itself.
There are pros and cons to each, and VBOX is a great piece of software, but it is more resource intensive than other options available.
What are the technical constraints on designing RISC-V chips with feature and performance parity to modern x86/ARM designs?
Just design constraints, not manufacturing, or adoption