You are suffering heavily from imposter syndrome. Because there are so few 150 person companies, most CTO jobs are for small companies. This doesn't make them

You are suffering heavily from imposter syndrome. Because there are so few 150 person companies, most CTO jobs are for small companies. This doesn't make them any less of a CTO job. In fact, the hard decisions for a CTO are often going to be at the start. Choosing the stack, building the initial team and engineering culture... So stop questioning yourself.