You need both deterrence and assurance. This is why I advocate equivalent numbers, but not more.That is obvious. It's what the Chinese military have been doing for decades, and what I've posted previously.
These comments still do not address your assertion that an excessively large Chinese military would deter the smaller ASEAN nations from embracing more trade with China.
Do you still believe this assertion to be accurate?
China already has the logistical advantage to the US in the ASEAN area. She also has land connection with ASEAN, that means any ASEAN nations that dare to turn adversarial towards China would face the wrath of China that the US would have no guarantee to protect. This is enough deterrence to the ASEAN.
On the the flip side, these countries would feel assured that China is not entirely unconstrained, because China does not have overwhelming advantage to let her get away with bullying or crossing the bottom lines of, for example, national sovereignty of these nations.
This is why I am very happy that the US has bridged its own Middle East Theatre and Asia Pacific to form the Indo-Pacific. This actually give China a lot more space to expand her naval forces. Now China could say that she has legitimacy in ramp up her navy to the equivalent of all of the US Indo-Pacific naval forces, and the ASEAN nations will only feel that those expanding PLAN naval forces are aimed at the USN.