Gaming VM and over-provisioning cores?

I run proxmox on an i7 10700 8c/16t CPU. I have this idea that if I have a gaming VM, I shouldn’t over-provision cores and even leave 2 for the host, but is that really the case. Can I somehow ensure VM is basically pinned to say half the cores, and the other half can be fought over by whatever other VMs I’m running and...