(Although on Linux as KVM/QEMU the same sort of thing should be observable on a W10 Host with VBOX / VMWare although these won't by nature of the virtualisation system used be quite so efficient - but still will be perfectly acceptable). You can see how tiny the amount of CPU is being used - these days VM's are very efficient (or can be) provided you don't go bonkers and run too many tasks on them concurrently. Here (although on a Linux Host) I'm running a Win2K19 Server and an XP system both as Virtual Machines. There's no problems running multiple VM's at the same time either - provided you have enough RAM. Your VM's can be stored on any accessible device(s) available to your system including Network shares if you want. On an SSD performance will be hugely enhanced. If you've got a spare SSD then why not have the VM on an external SSD - connect via USB->SATA connector to your machine. While I prefer (in general) VMWare to Vbox there should be no problem running a W7 VM from any device you like on VBOX or otherwise and it shouldn't have any interference with your current Host.

Windows 7 virtualbox arch