The idea that her navy can get close to Chinese coast to impose huge damage is just Childish. The first thing that Vietnamese navy will do in the first day of a war is: running out of the strike range of Chinese air force.
China has already attacked Vietnam and taken its islands. It is not the first time they are seeing Chinese take what belongs to them. The last thing PLA would do is to obliterate the country on the first day as it would result in worldwide blanket sanctions against China.
Are you aware the situation of Vietnamese armed forces?
Coming to strike air defense targets along the Han coastline? With merely 35 Su-30? Are you a Chinese agent?
They are not strong enough, but they will throw everything they have at it. Vietnamese can't rely on guerrilla war tactics anymore. PLA's speciality is non-contact warfare as they are well aware of their own weaknesses. If you are assuming that Vietnam is going to draw PLA soldiers inside Vietnam and repeat a Nam War, that's not applicable.
Watch who you call Chinese, mate. I am Indian and proud to be so. Dunno why the Singaporean flag is stuck to my profile as I logged in once from there during the travel.
And it will scare the crap out of Vietnamese leaders. Don't forget Vietnam is an export-oriented nation too. And her dependence on overseas trade is much much bigger.
Vietnam may be smaller and poorer than China, but it heavily weighs down on Chinese psychology. The CCP may not show it or laugh at it publicly, but it knows this reality. In no way will Vietnam defeat the PLAN, but they will definitely make it known that they won't go down without a fight.
In the entire Asia Pacific, if there is one other country that can stand up to the PLA in this region, it is Vietnam.
China would wipe the floor with Japan if PLAN would strike them today. Those shiny toys would be useless without war experience. All the Chinese have to do is to reach out to the US behind the scenes and assure them that no American soldiers/assets would be harmed.