Trip to China - itenerary and do’s/dont’s

As the title states my wife and I are looking at doing a trip to China in the second half of the year (thinking October some time).

We’ve previously done Europe for 3 months. This trip would be about 2-3 weeks - we are undecided at this stage just depends on how much we need to move from place to place.

We’ve done some travel and are happy to walk a fair bit to get around. Some things definitely in our rough plan are pandas in chengdu, the Great Wall, the avatar mountains and heavens gate. We love culture shock when we travel and traditional monument type things, also love experiencing culture through food, the natural environment and unique experiences.

Have a budget of about 15k-20k so not a lot is off the table.

Would appreciate any thoughts, tips, locations and activities that are your “must do’s”. Also anything to avoid or look out for - unsure around safety and food etc.

All suggestions, ideas and opinions welcome. Thanks for the tips in advance.