Both are official categories. Plutoid is another name for the ice dwarfs in the Kuiper belt out beyond Neptune. Ceres on the other hand is from the asteroid belt, and the only thing there large enough to have formed round, although some think Vesta might also qualify. So it’s the one case of a dwarf planet that isn’t a plutoid, though personally, I think “largest asteroid” is still the clearest way to describe it.
Personally I feel the reclassification of Pluto as part of a belt rather than a planet is part of appreciating just how much more is out there, and doesn’t need to mean neglect.
So as far as mnemonics go, for us people who like all round things I’d like to offer one I made a little while ago: My Very Excellent Mother Can Just Serve Us Nachos Or Perhaps Hot Quick Meals Eaten Slowly. For Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Orcus, Pluto, Haumea, Quaoar, Makemake, Eris, and Sedna. But if it isn’t obsolete yet, it will be soon.