I'm not even sure what "quintessential" means.
To me, an example of a bike boom model from that era would be the Sears Free Spirit 10-speed.
Even for a 15-year old with a paper route. I could afford and ride a "10-speed."
1. It was the beginning of non-Euro and non-Italian bike building going large-scale.
2. It was the beginning of marketing bikes to a broader mass target demographic, i.e. outside of Europe.
3. It was the beginning of a lot of things cycling, and led to what we have today.
4. It was the beginning of affordable (i.e. non-Schwinn), available, and possible.
I didn't even see an Italian or European road bike until my early 20's. The bike boom made me think about riding.
As far as the "top end," the Teledyne Titan is a good example of the 70's approach.
"Let's make a really light racing bike." "OK."
"Let's use Titanium." "What? That's for jewelry and NASA."
"Yeah, but it will be light." "OK, sounds good. Where do we get it?"
"The Russians have it." "The Russians? Really? We can do that?"
"Yeah, we can get it. It's about money." "OK, done."
"Wow, it sure is light." "Yeah, ain't it cool."
"Wow, it sure is fast." "Yeah, ain't it cool."
"What's that cracking?" "Um, not sure."
"Look, it's failing." "It sure is."
"Those Russians."