Speaking as an autistic person, and someone who usually never describes things as "cringe"…

Top is cringe.
Bottom is cringe too unless you're doing it specifically for awareness and educational purposes, with zero "look at me" motivation. Also I'm pretty sure there have been plenty of videos on Tik Tok of people actualy faking it.

Serious question, why would you film yourself stimming and post it online. You might as well film yourself scratching your nose for all the significance it has.

Like you said, bottom would more likely be for the purpose of awareness. I've seen a few cases of people with different disorders or conditions making YouTube channels where they film themselves in order to show what life is truly like for them and how it's not always like how it's portrayed in media. One I know of is a person with disassociative identity disorder (the disorder that used to be known as "multiple personality disorder" before people realized "personality" might not be the right choice of word) has a channel dedicated to the topic and showcasing what it's like being a "system" (the term used to refer to someone who has multiple identities sharing a body and brain).