So why are NIZKPs and ring sigs used when only one is required for anon? Anybody?
NIZKP are
part of the method used by CryptoNote ring signatures, which was copied by SDC. It is in section 4.4 of the CryptoNote white paper.
Do xmr and sdc have technically the same anon feature?
It isn't exactly the same due to the nature of the code bases (SDC is built on top of a Bitcoin fork, Monero is not), and there are some other small details that are different, but the overall method of the ring signatures is the same.
I could kiss you smooth. What's you take on the ShadowSendv2 whitepaper?
They should have properly cited cryptonote instead of just burying it in the references with no citation in the paper. Other than that, and ignoring the issue of writing quality and style, the paper isn't bad.
I'm told that the messaging thing is similarly derivative of Bitmessage with similar lack of care to properly cite and give credit, but I can't confirm based on my own research (since I haven't done any).