In regards to vCPU to pCPU ratios have a look at Scott Lowe's Whitepaper "Best Practices for Oversubscription of CPU, Memory and Storage in vSphere Virtual Environments"
"…for every additional workload beyond a 1:1 vCPU to pCPU ratio, the vSphere hypervisor needs to invoke processor scheduling in order to distribute processor time to virtual machines … experts suggest that vSphere “real world” numbers are in the 10:1 to 15:1 range. Still others indicate that VMware itself has a real world recommended ratio range of 6:1 to 8:1."
The whitepaper finds that
1:1 to 3:1 is no problem
3:1 to 5:1 may begin to cause performance degradation
6:1 or greater is often going to cause a problem
Also have a look at Find vCPU to Physical CPU Ratio with PowerCLI | vNoob, The script will give you the ratio per host, but best to change threads to cores, as hyper threading is generally best applied but ignored.
hope that helps