Detian Transnational Waterfall wasn't very busy when we visited. The main attraction was the river spanning two countries, with bamboo rafts from both China and Vietnam cruising on it.
Viewpoint No. 5 offered a great panoramic view of both waterfalls: the Chinese side is Detian Waterfall, and the Vietnamese side is Ban Gioc Waterfall.
You can take photos at the 836 Boundary Marker. Staff directed the queue and maintained order, moving quickly. You can even ask them to take your photo for you; they take pretty good pictures.
It's advisable to stay near the entrance. There's road construction on one section of the road leading to the scenic area, so drive slowly. If you're driving, you don't need to take the sightseeing bus. Parking at the scenic area costs 30 yuan per day.
The entire area can be explored on foot in about two hours. The scenic area isn't large. At noon, we even caught a folk dance performance at the Bronze Drum Square.
Next to the main scenic area is the Old Kapok Forest Scenic Area, where you can see the border line and boundary markers. It wasn't crowded, and there's a hotel inside.