If you want to move a VMware-based VM to an OpenVZ container, please refer to the Live migration of a physical machine to a KVM section. Note that it only works for Linux platforms.
To migrate a system to a KVM-based VM, you can use Clonezilla to copy the system content by referring to the System migration of a Windows platform section. Just remember that you have to remove VMware Tools if you have already installed them on the source VM.
Rather than cloning the content, we can simply import the virtual disk of the source VM because Proxmox supports the VMware format. Please note that the following applies to a Linux environment too; you just need to skip the Windows-specific options.
To enhance the performance, ...