Might try this method, which will cause a lot of grumbling from others.

Bracket your shots with the shutter speed around 1/250 or higher. Do not change anything and take at least 5 shots, maybe up to 10 shots or more. Make sure your camera is on a sturdy tripod (you can get vibration from the water if the falls are close and surging). Do this method for different locations of the same waterfall. Then, when you get home, do your post processing with stacking (this is not an HDR stack method since you have changed nothing). The only thing that changed is the water. When doing the stacking try it with 3, 5, 7 and 10 files, and you will find the right number of files to use. I really like doing this because you don't have a bunch of shake and no messing around with the ND filters. Good luck and if you do use this method I would love to see your results.

Looking for some techniques for creating that creamy waterfall look.
I will post what I do and others please chime in with any other techniques.
Posting some pics here and if you pixel peep you will see there is the effects of vibration or lens issue...not sure which. I was using my 70D with 24-70F4LIS lens so not the highest quality setup and I was in a rush so the trek guide pushed the button for me (2 sec delay). if you look at the little petals on the rocks you can see the effects of the lens or camera movement. Generally pleased given the setup time I had but I am not sure how much better they can be. I don't know what I should expect.
The tall waterfall was with a 5dMkiv with 70-200 on a tripod.
What would I do differently to get better/sharper pics?
(they are heavily edited in LR ...no Photoshop).

So far, here is what I do:
Tripod
ND Variable filter
Mirrorlock up
Triggered or 10sec delay (allow any mirror slap vibration or "human shutter button pushing" to settle out.
Tried to stay out of the wind. (there was very little to none)

Q:
1) How much does the quality of the tripod contribute to the shake? (I had my BeFree travel tripod which is well undersized I think.)
2) Would shooting with a prime make a difference in the sharpness? (ie I am expecting to much pixel peeping goodness from the 24-70 and the 70-200?)
3) Do I need to be using a 50mp sensor camera to capture more detail?
4) How much does the ND filter affect sharpness/detail (using a Hoya Variable ND circular filter)

Any additional tricks or techniques would be appreciated.

Thanks.

I have a question first of all - did you shut off image stabilization on the tall falls? On a tripod, that can cause blurriness as the camera tries to stabilize a stable image.
It appears to be a hazy day. Misty, perhaps. That will also give you the blur seen throughout the photo. Not a bad thing - I often get up on a foggy day and jump in the car to shoot! You will never get ultra sharp photos in those conditions, though. It is like shooting through a pane of glass with a slight fog on it.
Also, F18 could be less sharp, but to get the low shutter speed, probably the best you can do.

In the photo with the people, I see it could be a little sharper. Once again - image stabilization on? Is the ND filter introducing haze? Try some shots with and without and compare.

Last, yes, your tripod could do it. I have a MeFoto travel tripod and when I rented a Nikon D700 to try before deciding on my Olympus, I found that the tripod is definitely not up to the task of such a heavy camera. I got a much better, carbon tripod (Feisol) and not much will move it.