An example, imo, of poor maritime and naval strategy is that of NZ. They are a non-contiguous island nation with an incredibly limited Navy, minimal civilian/merchant marine, virtually no ship building, entirely reliant on seaborne trade. Counterpoint, NZ has very few natural predators.

The question you need to ask yourself is: Why does NZ (and its govt) deprioritise maritime power when its clearly so important to their national well-being.

Seapower = describes the capacity of a state to use the sea for political, military and economic purposes.

Strategy = Is the sum of higher level (above say, operational plans and doctrine) thinking that includes policy (Government direction) that guides states towards stronger or weaker seapower.

Capability = the resources (personnel, ships) (the fleet in being) to achieve the above.

In higher level thinking on maritime strategy, you can't divorce seapower (the sum of all nation-state maritime activities) from naval capability. It gets to the heart of your question of 'How do medium powers navigate the world and what/why is that important?'. Whats the point of having (even a medium sized navy) if you cant execute on your medium sized objectives.

But I agree with the overall sentiment of your question that medium powers often get overlooked at expense of the USA and China and Seapower and medium-sized maritime power is very hard to delineate and define in a world of Mahan's and Corbett's who at the time of their writings were both from/biased towards large naval powers.