What would sauron have actually done if he had actually succeeded and conquered middle earth? how would he rule?

I forget which video this was in, but it wouldn't have been too terrible. Once he had purged Arda of everybody who had opposed him, he would have lessened his grip a little and basically ruled like North Korea. Livable, not exactly favorable, but livable. Sauron's goal was not to subdue for the sake of subduing, but to establish order in the known world. His intentions are a weird twisted version of good, but his means are questionable at best.