Is it too late to go to the Summer Palace and the Great Wall in one day?

It's a bit rushed. The key is that it's not good to play in such a hurry. The Summer Palace is still worth spending more time.

It's okay, the time is about the same, I feel that the two scenic spots should be quite fulfilling after a day

In fact, as long as the transportation is convenient, you will be fine. Take a taxi or find a through train.

Solving the traffic will solve everything, but getting up early is for sure

It must be a bit rushed to go by yourself, it is recommended to find a group

You must not rush, the time of day is just right