I really like your 3rd build! It has good contrast. However, I do recommend to find a way to add non-copyrighted music to your videos, and try to turn up the gamma, the vids turn up sort of dark. Also, when recording, try to use a more playful tone or also known as a recording tone when making videos, it helps engage your audience more.
Other than the few things I mentioned, you are doing very well for a beginner! Don't take anything I say as hate, it is just constructive criticism.
P.S. you said "TheDiamondMinecart" instead of TheDiamondTnt :)