I am so sorry about your wife.I would have liked to meet her and look at her paintings.
I am honored that you want my advise as I only grope around and use my instincts as far as design and planning goes.
You are on the right track with your thinking design is like sculpture. I also felt it was like interior design but with plants.
There is a woman who wrote a book about "Color Echoes "
Pam Harper is well known.
Here is a blog about her gardens. I used a lot of pictures to give me hints as to which plants to arrange .
http://phillipoliver.blogspot....
This is her book on Color Echoes. Google her name and see if there are any You-Tube videos.
https://www.google.com/search?...
