I've advised 40+ startups on hiring, org structure, and leadership, and excited to take a stab at this question.

The key first is defining in more detail the role you need today and the role you aspire the company will need 12 months from now. Where do they intersect? What hard skills vs soft skills are needed at each juncture?

The real important part of this will be whomever you hire, will they have their domain in which they can make their own calls and have the final say while you're still there? Management overlap or disagreement is generally what causes leadership to be a mess. The best talent you'll want to attract will expect to have final say on many matters and not have to run so much by you.

As you mentioned, COO's typically have different skill sets than CEOs. COO's run the internal business and allow the vision set by the CEO to become reality. It happens, but not a guarantee than a COO can evolve into a CEO. Your typical CEO is busy setting the vision, meeting investors, building partnerships, brand, working with media, hiring, etc... In the case of many CEOs, they simply don't have the time to meet with their direct reports who lead the other business functions. Although it's prestigious to report into a CEO, most people are frustrated by the lack of time, feedback, and direction they receive. This is where a COO can add a lot of value; by having more time to manage, lead, and guide the rest of the leadership. This way the CEO can spend time with the COO, and the COO then pushes the right framework, expectations, and feedback to the rest of the org.

If you have any other questions on this matter, happy to discuss on a call.