I have a pretty good picture of the military posture of both those nations you cite and agree with you as to what they are. Interestingly both have made overtures to the US to reuse bases in their countries (as a deterrent to Chinese expansion.)
BTW, I seriously doubt China would attack Japan beyond a plan to remove their “navy” from the playing field. Japan is no military threat to them and has financially been a disaster since the late 80s. Those islands in the south china sea around which oil is in abundance is the prize China wants more so than even a reunited Taiwan IMO. Someone suggested, not you, that Japan may have nukes...there is no chance in hell they do unless they were supplied by the US and I don’t see that as ever happening.
China holds the cards here, a minimized US pacific presence, regardless of the “lets pivot to the Pacific latest obsurd strategy coming from DC”, and little opposition in the Pacific including Australia means the game rules are set by them, not the US, not SEATO, not the UN nor Japan. Hopefully they use constraint rather than muscle. China could live with a loss of 100 million people, the US cringes when someone gets hit by a car.
The Japanese Maritime Self-Defense Force is quite capable of defeating the PLAN in a straight-up fight, without help from anyone else. Across the whole of their force, their level of technology is better and they're certainly better-trained. There's a high danger of a VERY embarrassing defeat for the Chinese in any conflict at any level.
Don't be fooled by the name; the MSDF is probably the second-most powerful navy in the world right now.
Yup