One or more virtual processors can be defined in the VM but cannot exceed the logical processors (sockets x cores x 2 if hyperthreading is enabled) present in the host. The number of vCPU sockets specified in the configuration determines the number of cores available. One VM could have virtual sockets and virtual cores, but this choice is mostly for the licensing of OS per application limitation (for example, the latest SQL Express can work with more cores, but not with more sockets).

With more than eight vCPUs, virtual NUMA (vNUMA) is enabled and ESXi distributes the VMs in more NUMA nodes, if it is not possible to fit in just one. Now, memory hot-add also works well with vNUMA. For more information, see https://blogs.vmware.com/performance/2017/03/virtual-machine-vcpu-and-vnuma-rightsizing-rules-of-thumb.html.

The maximum supported vCPUs per VM is 128.