Speed wise, water is going to fall at the same rate as gravity pulls anything else down. You could put some simple particles into the scene with gravity enabled for reference and try to match up the speed of the panning with the speed of the particles falling. Some modifications to the UVs may be necessary as well, in which case you may want to do the same kind of hack setup reference with particles in whatever tool you used to build the meshes.
For the smaller waterfalls, the biggest issue for me is they kind of sit out away from the main body of the waterfall, but seem to have way too much water for not really cutting into the main falls that much (or at all?), and they themselves fall pretty much straight down. You’re never going to see something like that.
If you look at some reference you’ll see that any kind of rock in the path of the falls are going to cause the water to fan out or outright split the water in two. Water is strong, and anything that’s just a shelf like that is going to quickly erode away, so it’s has to be a big strong rock jutting out cutting the water apart, or a much more significant land mass. Or it needs to be much higher up in the waterfall where the water has less speed.
You can see there are smaller rocks near the top, some larger protrusions that really split the flow of water maybe a third of the way down some of the bigger falls, and after that there’s nothing until it hits a much more significant “ground”.