I would be wary of taking advice from a CEO who cannot fire his cofounder. Technically that means he is not the CEO and there is no one explicitly in charge of the company.
In early stage startups, the title of CEO has more to do with who's in charge of vision and runway and less about org structure. Decisions are usually made based on an equity stake.
That is most definitely not the case for most start up companies I work with. Not have a CEO day one who runs the company is usually a sign that you have not started a company before.
Most C-Level employment decisions are made by the board on behalf of the shareholders. Many new companies do not have a BOD yet, so the shareholders will have 'direct' representation. Extremely early stage companies will have all of their shares split between the two founders.
The mere presence of a "CEO" title doesn't grant one founder domain over the other(s), and it shouldn't, but this helps explain the frequency of founder drama.