Renewable energy cannot be blocked as easily as the Malacca Strait can be
You are right about China keeping options open - the BRI initiative is about improving land transport options in Eurasia.
Also, the US Navy can project a lot of power into the Indian Ocean and Western Pacific.
Beijing's being worried about an interruption of it supply of oil would explain why they continue to build coal generating plants at a fast rate in addition to solar plants. (China has plenty of coal.)