Need help stocking a 20 gallon?

I LOVE FISH! alright i recommend definitely getting a cory cat because they are excellent bottom feeders and simply unusual. If you get a tetra remember you should get at least 3 because they are community fish. I would recommend getting a phantom tetra or possibly a septer tetra. Skirts are cool too. Platies are legit. Screw guppies they are so fragile. I swear i put them in excellent water conditions and they died in a months time. My aunt had them in crowded bowl and they were thriving. Everything on your list is compatible so its simply up to you.