Not really. It is mostly because the people online find something suspicious and report, then the constabulary will start investigate at that specific target. Do you really think that there would be enough people to monitor about 1.4 billion people every second? It is more like the company that the program you are using is recording your data. But of course, if someone posts something harmful to the society like nudity, pornopraghy, hate, breaking the national security, spreading fake information, drug business, insulting ancestors, gambling, etc. These will literally get the criminal charged immediately. Basically all the illegal things. Actually regardless of the CCP, I think people outside of China should "care" more about the F,B,I. XD China isn't strong enough nor have enough time to watch 1.4 billion people and including y'all outside of China at the same time XD.

In one word, if you are not guilty, living in China is completely safe and even much safer than most other countries. Welcome to travel to China someday when you have time. People in China are very friendly to friendly foreigners.