Once you've delegated nameservices to DreamHost, everything beyond answering the question: "What are yourdomain.tld's nameservers?" is answered at the DreamHost nameservers and managed at DreamHost.
Yup, all through your control panel at DreamHost. Note that you can additionally forward subdomain DNS to another nameserver. I've actually been thinking about whether this could usefully be used in those situations where you want to manage a domain somewhere else but host the subdomain here at DreamHost.
Anyway, hope that answers your questions. If you have any ore specific questions, just let us know!
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