Is it wrong for me, as a neurotypical person (AFAIK, there have been hints that I might have something undiagnosed), to use terminology coigned by atypical people? The way f’example stimming and overloading have been explained to me describe things that I do and the reasons behind them really well, but I don’t know if it’s appropriate for me to call them that.
Most people who stim a lot and get overloaded a lot are autistic. Most. Not all. Some people with ADHD also experiencing stimming and overload. So do some neurotypical blind people. So do other folks.
Overload and stimming are words that describe particular experiences, not a particular diagnosis. If you have those experiences, it’s ok to use the words.

Or if you are referring to them in other people who have them. I really don’t want people thinking that they can’t refer to me as overloaded just because they don’t experience overload. Or that they can’t refer to “stimming”. Basically, they’re words. The words exist to refer to things. They aren’t “slurs”. It isn’t “reclamatory usage” which has to be under special restrictions to keep bigots from using the words too.

Note, BTW, that there’s a lot of overlap between “some autistic people…” and ADHD, and “some ADHD people…” and autism, possibly because they have high comorbidity and people don’t always get diagnosed with everything they might possibly have.

I am 90% sure it’s also possible to induce sensory overload on neurotypical people, it’s just NT people have a higher threshold. I don’t remember where I heard it from but I could have sworn there was some scientific experiment where they were testing the senses and ended up overloading the NT people involved and it was a universally awful experience.

My guess (correct me if I’m wrong on this) is that nearly everyone stims to some degree (it’s just called “fidgeting” at low-key levels) and could experience overload at the right conditions. Just with some differently wired brains stimming is more frequent and intense, and the threshold for sensory overload is lower. Which would explain why there are people like me and presumably op who have a number of “autistic traits” but do not fit the ASD diagnosis. 

All of this.