Of course, the People's Republic is a very different state to dynastical China, with notably different leaders and a very different ideology.
You are right that China has historically made a point of not interfering in other states' affairs (an approach that the current leadership continues to champion) but the current tensions with Japan, Vietnam and the Philippines (especially the latter two) are mostly territorial disputes and thus are often framed as a question of China's national sovereignty. Therefore, China's leaders could provoke a war with Vietnam in the South China Sea while continuing to spout all that 'mutual respect for sovereignty and territorial integrity' stuff.
shickingbrits wrote:Beating up non-nuclear countries can be quite costly and only serves to further the interests of the military and their suppliers and a small handful of private interests
Conflict could be used as a way of boosting the legitimacy of the CCP's one-party rule, and the issue of legitimacy is an important thing to consider when trying to understand the government behaves the way it does. The unspoken social contract of the reform and opening up era was 'accept one-party rule and in return get steady economic growth', but the reforms that have been undertaken have made the central government less and less able to claim responsibility for economic growth (which is more and more driven by local government and the private sector). So how else to continue claiming legitimacy, when you are unelected? Being the big, strong protectors who guard China against foreign threats would help. Would they go so far as to provoke a minor war to help with this? Maybe, maybe not. Might their increasing belligerence trigger a conflict by accident? Also possible. It seems unlikely at present, but the possibility of something silly happening in the future cannot be entirely dismissed.