This thread touches on some of these concepts and is worth reading for anyone who wishes to refine their builds.
I agree with what you both have stated but would like to add what I consider effective:
1. Plant in odd numbers - 1, 3, 5, etc. If it's a feature plant or is very eye-catching, just use one.
2. Avoid using a great variety of Neoregelia cultivars. I see a lot of hobbyists using many types of Neos with different patterns and colors and IMO, it looks garish and unnatural. Use one cultivar or species and plant 3 or 5 of them. If your frog species is terrestrial and/or doesn't use bromeliads, don't use them at all. They look unnatural enough only inches from the ground when they've evolved to grow in the canopy.
3. Allow yourself 1 or 2 "feature" plants that will catch the eye. The other plants in the viv should complement these and bring out their interesting aspects, i.e. they should be comparatively more boring. Too many interesting colors and textures tend to overload the senses.
4. Use rule of thirds to create focal points, then place specimen plants e.g. miniature orchids, interesting aroids, etc. at these points. A shingling species would look nice climbing of the two vertical "thirds"; this goes hand-in-hand with asymmetry. Never plant something right in the middle of the tank, especially if it's your feature plant.
5. Use your background to create lines that draw the eye toward these focal points or other areas of interest.
6. Set a realistic number of species planted in the tank. The best tanks are those that utilise a minimum number of species but allow those plants to fill in and colonize the area. The greatest variety of plants should be found growing epiphytically on the background. Dwarf species of Microgramma, Pleurothallis and Peperomia all make a mossy background look very alive.
7. Don't use moss as a floor. It's unnatural and has no benefit for the frogs. Moss for the background, leaf litter for the floor.
8. Know the growth habit of your plants. Use this to plant them well so they mature and fill in properly. Consider the mature size of your plant as well.
9. Don't use creeping fig.
10. Be patient. Give your tank time to grow in. This ties in to overplanting at the start. I don't consider any of my builds "done" until each plant and patch of moss is grown in exactly how I want it. This can take months to years.
Edit: Here's another thread relevant to the topic:
Design Principles