I was stealth in high school (except to those who had known me from freshman year/middle school) and am stealth in college currently.
If people touched your chest, did they notice the binder? No. I have been moderately felt up on a few occasions and no one has noticed. Obviously, if you are a D cup, things are different.
If you've hugged someone, did they notice the binder then? No.
And if you pack, and someone touched it through jeans, did they think it felt real? How about through sweat pants? (btw, what packer do/did you have?) Do not pack, I have been kicked in the crotch before without questions being asked.
Did you come out to anybody and if you did, how did they react? It depends on the person, and I will only come out to people who I know are queer-friendly so that biases my experiences. One of my ex-girlfriends barely blinked and went back to making out with me. One freaked out and dumped me on the spot, but a week later, she got over it. Most people just take a mental step back, probably ask a few questions about what it really means, how does it work, etc. and just move on with life. In my experiences, after the initial coming out, people often forget that you are trans. Funny enough, I have had to re-come out to people because they had simply forgotten.