Did Mount Everest give any advantages to the ancient Chinese people?
All of the mountains, including Mt. Everest, helped protect the ancient Chinese people from invasion. There were very few ways to get into China and all of them were difficult.
In general, when referring to the entire population as a whole, you would say "the Chinese are an ancient people". To say "Chinese are ancient people" leaves the reference population undefined - are you referring to the entire population of China or are you referring to a select group of Chinese individuals who are older?