It sounds like you shouldn’t go to a startup. I’ve done a mix of both (from #1 hire out of 2 total engineers all the way to a Fortune 25). Across the board, I’ve found the smaller the better (more enjoyable, more learning, more energy, more urgency, better colleagues).
Yeah, there’s no formal time laid out to do step X in the course of development. There’s the chance that you won’t make payroll someday.
It’s definitely not for everyone, but when you get a good team together on a good project, it’s fantastically energizing.