What would these words be called, and are there any related rules on how to use them and what they each mean?
They are exclamations.
a word that expresses sudden pain, surprise, anger, excitement, happiness, or other emotion:
"Ouch," "hey," and "wow" are exclamations.
Exclamations (also called interjections) often stand on their own, and in writing they are usually followed by an exclamation mark rather than a full stop:
Ow! That hurt!
Aren't they interjections?
According to the Wikipedia article, this category includes exclamations and hesitation markers as well.
Linguistically, they can be called vocables:
a sound that is used in a particular language, especially one that is not considered a word, for example a sound such as "la" used in music or an exclamation such as "huh"
Another word which may be a little bit more recognizable outside of a linguistics context is vocalization/vocalisation, which means
a sound that is produced with the voice, or the act of producing sounds with the voice
although that has some other, unwanted meanings, including the addition of vowels (e.g. to Hebrew text which is written without them), the calls of animals, or as a synonym for "speech" in general.
filler from Lexico
1.4 A word or sound filling a pause in an utterance or conversation (e.g. er, well, you know)
- “English speakers tend to fill pauses in our speech with ‘um’ and ‘er,’ but speakers of other languages use different filler sounds.”
I would like to say that they are not even words, and the more accurate way to represent them would be to call them as "sounds". Because each of these can be classified into one or more categories of the English language. I would also like to agree with Hobbs, who said that they can be called as vocables. However here the thing is vocables are for one language. But I would like to call them merely as "sounds" because no matter where you go, which language the people speak, they still remain the same. "Non-words" as the OP put it, will always stand for the same meanings everywhere
They are technically called onomatopoeia's, see here for a list of examples.