Can someone give me a good explanation of what the DNS Settings checkboxes are used for when setting up a new account with the WHM? I can't seem to find any documentation for either of these options.

If I'm creating a new site for someone whose domain is parked somewhere else, and I don't want the domain to point the the new site until it's complete, I'd think to check the "Use the nameservers specified at the Domain's Registrar (ignore locally specified nameservers)" checkbox. Once the site is complete, I'd change the nameservers specified at their registrar to mine. But if I've checked that checkbox, is everything set up correct on my own server, or do I then need to change something on my server for the site to work correctly? I can't find any way to change this setting once the account has been created.

What happens if I don't check it (so the account is created to use my nameservers), but they don't change anything at their registrar? It doesn't seem like it would do anything in that case.

And while I'm here, what does "Overwrite any existing DNS zones for the account" do?

Thanks!