You can be a dominant power in a region without invading other countries.
For example: the US in the Americas.
China was a cultural and continuity powerhouse. And that they controlled such a geographic span as they did given their location on a more or less open plain—just like India—is very impressive.
Both giants used a sophisticated mix of soft and hard power.
Oh, and ask the Vietnamese about Chinese invasions.
“You can be a dominant power in a region without invading other countries.”
But they weren’t. They weren’t even interested in interacting with these other cultures.
Vietnam and Korea were simply the same people, same culture.
The fact that they became separate actually argues against Chinese dominance in that they couldn’t even keep their people at the peripheries.