The males need a place to go rest out of sight from each other. It is more than a matter of esthetics. It is very stressful to them to not be able to retreat to a place they where they feel safe. In addition Betta do like to have a comfy place to sleep. IME the preference is a soft leafy spot near the water line.
I don't personally have any objection to artificial. If there are no live plants to consume the wastes, I usually try to keep the substrate pretty shallow, so it can easily be cleaned.
But other than those tips, I think your boys are lovely. And I like fufu stuff sometimes, myself. Good idea about the solid insert for the boys. They will usually hide though if provided a retreat.