What means of transportation should I use from Nanjing to Chongqing and Chengdu? Recommended plane or high-speed rail or self-driving?

The bullet train has been opened to traffic, which is a bit long but relatively good. I personally recommend the bullet train.

Driving is very troublesome. The road conditions of G42 and G50 in Hubei are not very good, there are too many mountains, and the speed limit of many sections is 80 or even lower, so driving will be particularly tiring.

It is also a pleasure to see the scenery in the mountains on the train, which you can't see on the plane.

Chongqing's light rail, subway and bus are particularly developed, and you can reach any scenic spot by car, and the main scenic spots are in the urban area. Chengdu is almost the same, and the bus is very developed, so you can take the bus. There is also a bullet train between Chongqing and Chengdu, which is faster. Or suggest you take a train to Chongqing and rent a car to go out to play. At present, the more reliable car rental agencies are not expensive, and the average car is less than one day in 200 yuan.