Hi Syl,
you can use PowerCLI to change a specific setting on multiple VM's. For example to change the number of virtual CPU's from one to two on all VM's in cluster MyCluster you can do something like:
Get-Cluster MyCluster | Get-VM | Where-Object {$_.NumCPU -eq 1} | Set-VM -NumCPU 2
Which setting do you want to change?
Regards, Robert