i am on the spectrum, but other than bouncing my legs when sitting and being stressed, i don't really have any outward symptoms that make me stand out. I would not know what to do if i did - i am lucky,
where i do stand out is in my dealings with other people and how i deal with stress
the posts above are correct, you can learn how to fake 'normalcy', and as an adult i have, but it comes at a price though,
i am older adult, and only got my diagnosis a few years ago,
as a result i was forced to learn how to blend in,
however, by forcing myself to act normal all those years and not respecting my limitations, i have driven myself into a burnout, have been off work sick for almost a year and got fired recently
basically i had built my life around a lie by denying my own needs
after my 'construct' collapsed, i have come to realise that honesty is the best policy, firstly being honest and accepting of myself, and then choosing an environment where i can be honest with the people around me
i am lucky that i am high functioning, the label of autism helps me understand my limitations and strengths, but it does not make me feel like victim or define me as a person, it doesn't keep me from being intelligent, having a good work ethic, being kind and respectful, being helpful etc
i'm trying a different path now, i accept who i am, i don't feel bad about myself or my limitations but try to focus on my strengths and on those people, employers and environments that play to my strengths, like all things in life you have to take the bad with the good, everyone has limitations and has to learn to deal with them best as they can
like a person with bad body odour uses deodorant t avoid 'offending' other people's senses, i am trying to understand that the way i communicate with others may offend them, so i try to keep that in mind when speaking but by having been honest with them about my challenges i expect a bit of understanding if i miss a signal
re NT's and 'normal' i think you may be surprised how many 'normal' people are unhappy, normal people can be shy, awkward, introverted, depressed, have overly sensitive senses, struggle with their personalities and not fitting in, have trouble finding good friends and a partner,...
referring to the start of your post, i would challenge you to propose a generally accepted and historically stable definition of 'normal' that applies to all layers and ages of the global population
i don't know in what country you live, but it is also worth noting that different cultures respond differently towards shy, reserved, introverted personalities
i say this because i have lived in many countries during my life and have experienced anglo saxon, germanic and mediterranean cultures.
personally i would guess the US is the absolute worst place to live for these personality types
society and the media tends to convey a world where everyone looks perfect, is a success and has tonnes of friends and partners vying for their attention etc etc, this however only exists to play on your survival instinct to want to belong, because being in a group is safer - it's manipulation with the purpose to sell product, not life
i'm happy to share experiences and lessons learned if you wish
ps if i sound patronising i apologise, i guess that people speaking from experience always sound that way