I already wrote about the lower & NW sections. The Northern one is almost as fun as the latter and less difficult.
Starting from the same MTR station an alternative plan to Ma Dai stream. Not as spectacular but cleaner and with less people in the falls.
Qiu Feng stream(秋楓石澗) is a cute easy one that can be hiked on its own upwards or as an end of a long day starting on Double Deer or Tin Mei streams.
Twin streams in Saikung country park. Dry in cooler months, really pretty after several days of rain. Climbable in hardcore or easy ways.
Quite close to Tung Chung, another way to go up to the Buddha temple within crystalline water and challenging jungle waterfalls.
A brief introduction to a really fun activity that you can do in Hong Kong, enjoying the summer heat outdoors.
Imagine Ng Tung Chai but steeper, with no “civilized” paths or people and more waterfalls. That’s Dai Sek or Tai Shek. Dangerous though.
Good initiation stream hike. Gentle slope, tons of easy exits upwards, incremental difficulty, pristine water, some nice waterfalls.
Lower Shing Mun reservoir provides a nice short stream and adventure hike. It can be added to a day of tunnels or others above.