I floated all the shelves in my kitchen this way. No strength concerns!

Those look great! Did you mount a strip to the wall then mount the shelves over it?
Basically… In my case I used the “single” version of what you posted. I’m sure the “strip” would be great, but didn’t work with my particular dimensions. Make sure you get good engagement with the studs in the wall and you’ll be fine. What is the actual shelf you’ll be using?