When you upload a new zone it will be assigned a set of nameservers - four. You can't choose what they are in advance, and you can't specify the TLDs. So you might end up with "ns-1933.awsdns-49.co.uk.", "ns-1109.awsdns-10.org.", or similar.
Does that answer the question? I'm a little hazy on what you're actually asking.
Old DnsMadeEasy customer here (used them for several years before moving to AWS). They were rock solid. We used them for hosting DNS for major cruise lines (fancy, very fancy ones), as well as other large Fortune 500 clients.
Their interface is pretty bad, but the backend is hardy.
actually, what i think is.. they're as near 'free' as it gets, probably. at least there's no up front cost using them. then its a lottery as to when u need to pay them to revoke... it could still end up cheaper than paying yearly fees for other certs, i imagine.. total cost of ownership or something..
It's a shame the containers appear to be stuck at 1 container per VM, which is fairly limiting, there's no real reason why you wouldn't run 10 or more containers on 1 VM other than IP allocation (which AWS already does very well)