Were there more “out-of-universe” or “JK Rowling-made-up” magical creature types/species in Harry Potter universe?
By “out-of-universe”, I mean creatures that exist(ed) in folklore/literature/fiction outside of JK Rowling (JKR) books – such as vampires, mermaids, phoenixes, grindylows or dragons (as opposed to kneazles which JKR invented).
In other words, did JKR invent more magical creatures than she borrowed wholesale from other works/folklore?
The answer should be based on precise count as opposed to random estimate.
Ideally it should include a full list of creatures counted as either “out-of-universe” or “made up”, or at least a reference to existing breakdown.
The count needs to include full JKR bestiary – e.g. 7 HP books + supplementals (especially Fantastic Beasts)
No need to list anything but the creature's name (e.g. no need for details, which book it's from etc).
You can choose to either include or ignore creatures considered mythical/non-existant in-universe, e.g. Nargles; if you include them, it's better if they are tabulated separately.
If the creature shares a name with a "real world" magical creature but is very different from any established descriptions, it counts towards JKR-inventions (personally, I don't recall any examples of this outside Garden Gnomes).
Plants are out of scope.
Real world animals with magical properties (e.g. Nagini as magicked up snake, or the python that Harry spoke to in HP1) are in scope, but obviously count towards "out of universe" column.
Real world animals that clearly have no magical properties (e.g. random birds, or dogs in privet drive) are OUT of scope.
Mixes/hybrids can be counted however you want as long as you state what you did, unless there are more of them on the list than the margin of difference. (I doubt that there are enough to affect the summary answer). Hermione's half-Kneazle can be counted as a Kneazle.
Sentient species (Centaurs/Goblins/Trolls/Giants) are in scope but all of the 4 listed here are clearly not JKR-invented. I don't know if HouseElves as JKR describes them exist in folklore.