Do the Night Prayers suffice for the regular Sunnah prayers, or does each have a different ruling, and what is the ruling on one who abandons the regular Sunnah prayers?

The Prophet, may Allah’s prayers and peace be upon him, used to make up the night prayer if he missed it, and it is an independent prayer. This indicates the desirability of preserving one's regular devotions (awrad) and making them up if missed.

As for the regular supererogatory prayers (Sunan Rawatib), they are among the most emphasized voluntary prayers. Whoever abandons them is not sinful, but he has deprived himself of a great good. This indicates their great importance and the significance of preserving them.