Hello,
Finally I sorted out, some how. I noticed that the topology settings for the cpu are not injected in the domain XML when the VM is resumed. So, when I modified the cpu and vcpu fields for an existing VM the Windows did not seem to care, showing the same number of sockets and virtual processor as during install (I think).
I took an approach very similar to what was suggested in How to set number of VM cores (use cores instead of sockets)? and everything works as I want, now.
Thank you for your answer, I think that this matter can be closed now.
Kind regards,
Adrian