For a broad brush overview of how it is perceived that each nation is framing its policy for naval forces, the foreword to the latest edition of Jane’s Fighting Ships is probably your best bet, and comparing them year by year is an interesting exercise. As regards any of the western navies you can find out quite a lot by reading through well-regarded but unclassified magazines, such as United States Naval Institute Proceedings. However, for the emerging Chinese navy – strictly speaking the People’s Liberation Army (Navy) – if you can find out anything concrete about their tactics & strategy then I am sure that your national intelligence services would be keen to take you on as a paid consultant!