Dividends will be credited to either your NRO or NRE account, depending on which one you have linked to your DEMAT account. To learn more about the differences and benefits of NRE and NRO accounts, read this article.

If you currently have an NRE account linked, you won't need to open an NRO account to get dividends, and vice versa.

The RTA is responsible for crediting the dividend (Registrar and Transfer Agents). It's possible that they won't be able to credit the dividend to your NRE account in some situations. A check would be issued to your registered address in such circumstances.
Both NRE and NRO accounts will be translated to separate DEMAT accounts in cases where you have both. So, depending on which DEMAT account you hold the dividend-paying stock in, and the bank account linked to it, either NRE or NRO will receive the dividend credit.