yeah ik, but most generic fantasy manga usually group them together, which is why I was surprised that this one actually does separate them
In web novel at least, the authors seems to have got a consensus about how to use the terms for those 魔 creatures.
魔族 is used to refer to a humanoid species, just like human, elf, dwarf. Translation also seems to settle with "demon".
悪魔 is for creatures from different plane, and translators commonly use "devil".
The fun came when 魔神 got translated as "demon god" because in term of species they're usually closer to devils, but demon god just rolls better off the tongue compared to devil god.
魔獣 usually refers to lower level magical beasts that looks like animals. While 魔物 can be more wide in definition including those weird things such as tentacle monsters.
Although TenSlime also use 魔人 to refer to monsters with human shape (but not referring to a single race).
The magics are more headache inducing as the WN authors don't seem to have anything as guideline (unlike DnD rulebooks who has guide on subtle difference between magician, wizard, sorcerer, warlock, etc).
So good luck with choosing the translation term when stuffs like 魔法, 魔術, 魔導 all got used in a single series.