DNS Clustering Questions

I"ve read through a few past threads regarding DNS Clustering and just GD a couple of questions if anyone has the knowledge to share. I am planning a new dns cluster that is intended to be spread across 5 North American Geo locations and 5 European Geo locations. My question is, in this case, do I need to create 10 total dns name servers to use for this or can I create duplicate instances in the 10 locations providing the backbone for a typically seen setup, for example dns.domain.com and dns2.domain.com and each domain name server has its own instance in all 10 locations. I am still in the planning stages of creating this and want to make sure I am going about this correctly and understanding the architecture behind it. As well, when converting existing cPanel web servers over, will these go through a DNS propagation period and will I need to resynchronize existing dns records? Lastly, when switching existing cPanel servers over, I read that you set these to a standalone setting and only the clusters themselves to synchronize. I want to make sure I am understanding this correctly. I really appreciate any help with this, just look to clarify a few things before I start setting up this cluster configuration.