What are the points one can discuss in a sync with the CTO of the organisation?

Any C-level person in a company will have a much higher level vision for the company and the CTO for the technology organization. If I were in your shoes, I would focus on trying to get an idea of how they think about their vision for the company/org. Based on the company size, in most cases they'll not be able to dive into details of your daily projects. The other thing you can do is to figure out how you can provide them with value so that you can keep meeting them, maybe once a quarter or once a half? I've been able to talk to C-level leaders about systemic issues that I see and give them my recommendation on how to address it. Be sure not to spend the whole time just complaining about things, that's not as useful. Identifying 1-2 things that you would address if you were in their shoes is far more important. Ensure that you are thinking about the "global maxima" not just solving the problem for you or your team.

Hope that's helpful!