They look good for the most part, but I would make a lot of changes to the plants. Small schooling fish like what you are planning thrive in heavily planted tanks. To all of your tanks I would add floating plants and just more plants in the substrate in general. The floating plants will help subdue the light and make the tetra and gourami look better.
In the 20 gal, you should have at least 5 corydoras as they do best in large groups. Just like the tetra, add as many of them as you can. The two schools in the 30 gal and 20 gal might look a bit crowded in my opinion. In the 20 gal it might be a bit overstocked. I'd rather just have a single large school of around 12-15 tetra; the more of the species around, the more brilliant the tetra will be. The dwarf gourami would also not be my first choice. Due to many years of inbreeding they are rather fragile now. They are also known to carry the dwarf gourami iridovirus, an incurable, fatal disease. Honey gourami are a much better alternative.
And lastly, while zebra danio, gourami, some cories, and some rasbora are rather adaptable to a wide range of water parameters a lot of tetra species aren't. In order to say that which ones would be best for your water and your tanks, we'll need your local water pH and hardness (both GH and KH). Sometimes pet stores will know these, but more than often you need to look at your city water quality report to find these. The water quality reports are often published online.