Wow! These are gorgeous images and worthy of hanging on a wall, printed BIG.
Your question is a little too open ended and you are probably setting yourself up to 101 opinions from 101 different people. Instead, let me give you one trick that I have done with images and critique yours under that consideration.
Let me preface this by stating this is a trick for processing images, not so much as for composition and exposure, as you requested. Although by way of analysis you will see how it can be of use in future images. It begins by reducing your image to values of light and dark. My prefered method is to simplify it to three values (dark, mid and light tones) but for this explanation I'll simply reduce it down to two. You'll still be able to see what I'm getting at. Here is your first image reduced (and with some annotations).
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As you likely know, our eyes travel to the lightest areas first. In this case, the water itself. You can see the flow
of the image in the blue arrow I indicated. The first thing I notice is that the eye travels beautifully in the prefered method most Europeans are comfortable with; top/bottom, left/right. However, there is nothing at the bottom right to bring the eye back into the image. My eyes follow the falls down and out of the image. The only thing that brings me back is that I was asked to really look at the image. A casual viewer would not give it a second glance (more than likely), even though it is an undeniably gorgeous photo. Remember that it is up to you, the photographer, to show
the viewer what you want them to look at.
The other nice thing going for this scene and its composition are the leading lines that pull the eye into the 'start' of the image (indicated by the yellow arrows). On first viewing I was immediately drawn to the top section of the falls. Compositionally, I like that the start was placed (almost) on a power point in the rule of thirds. Maybe just a hair more head room above the falls would have served the scene better, but that's for the next time (or a recrop if the original has it).
The final part of this analysis I immediately noticed, and it correlates with the eyes being led out of the frame, and those are the areas I circled in red. We already mentioned the water at lower right pulling the eye down and out but the rocks and the hillside also do the same. They are brighter in value in comparison to the darker tones of the river rocks and ledges forming the path of the water. Basically you have a ribbon of light against a path of dark surrounded by midtones. What further hurts this image is that the areas circled in red are in the corners furthest from your starting point. All this does is encourage the eye to continue its travel out the image on the opposite side.
Aside from the nitpick of headroom above the falls, compositionally this image is great. It has a nice diagonal flow that travels naturally, a strong subject matter, no distracting elements, lots of detail without it being annoying or cluttered. Exposure is dead on though some may find it a bit too flat. I know you didn't ask about processing but, as I see it, that's the only real problem here and that can be fixed easily with some judicious dodging and burning.
Just my two bits. I hope this helps.