Why do you think that you won't live up to your potential anywhere but a megacorp?
That's probably exactly backwards. Their external images is one of geniuses, but is just a marketing projection built on how much can be accomplished with huge numbers of work-a-day people cranking away.
When you get hired into that sea (especially as a fresh grad/young person), the system is designed to minimize the harm your untested and untrusted self can do. You'll be allowed to function at a competent level with the possibility to shine in all the predefined ways the system allows, and none of the ways it doesn't. I say "system" because the output of the bureaucracy, company policies and internal politics never lines up with how management thinks their company works. It's not (necessarily) malicious, but believing something is different from understanding it's feasibility or the actions that would be necessary to make it true.
A smaller company will have much more apparent ways to provide value to the company, and to grow your skillset into something even more valuable to them. Everything that needs to get done isn't already being done 100x better than you could by the department of doing that-thing. If you can sit down and get it done, that's way more of a personal accomplishment and job growth potential than if you were one of 10 people in the that-thing department at a megacorp.
What working outside the giants (specifically the giants that brag on themselves all the time) lacks is exposure. At Google someone can make a minor, not-that-genius, change to a product and immediately impact a non-trivial percentage of internet traffic, or put something into billions of people's faces. They can get go around smugly telling others how big of an impact they make to the world. But that's confusing their accomplishment with something google did without them, it's not "living up to potential" it's being a hanger-on.
