Use each for what it's good at. Your Nex carries your name, for the people and places where being known helps: friends, work, your town. Your Nyx is an alias that keeps its own name, followers and history, for questions, opinions and interests you'd rather not attach to your name.
An alias isn't the same as being anonymous. A Nyx is stable: it builds a reputation over time, and other people recognise it from one post to the next. Research suggests that stability matters. A study of 45 million comments on the Huffington Post (2013–2015) found that discussion was more thoughtful after the site moved from easy, throwaway anonymity to stable pseudonyms. When it later moved to real-name accounts, discussion got worse again, though not as bad as at the start. The authors say swear words are a crude measure and they don't know exactly why it happened. Still, it fits what Nyx is for: an alias you keep, not a mask you throw away.
Two things are the same for both:
- The rules. Community Guidelines apply to Nex and Nyx alike, and enforcement covers the whole account (see “What happens if my Nyx breaks the rules?”).
- Nixyum knows the account is yours. Other users aren't shown the link, but it exists inside Nixyum (see “Is Nyx really anonymous? Does Nixyum know it's me?”).
What you post can still give you away, so keep the two apart if that matters to you (see “How do I keep my Nyx separate from my Nex?”).