VM reservations will fulfill all these requirements since it will put the VM in front of the line during CPU scheduling and it calculate the memory access differently thus giving priority access to the memory.
It will not impact the other hosts or VMs unless you have HA Admission Control configured for a number of hosts. And since you don't have HA nevermind that ![]()
Since you don't have DRS the VMs will stay there unless moved.
Neither of these options (CPU Sharing or Affinity) will give the VM preferred access to resources and should not be used as such. It just for there corner cases where you need extreme tweaking capabilities.
Its just more controlling the location and the noise of VMs could have on the specific vCPUs for those "special" VMs.