You may want to consider a bigger tank for an adult peacock as it will provide a lot more entertainment if they have plenty of area to explore.
That being said, I would keep the one you have as she/he seems very entertaining!!
I am guessing whoever said that was misinformed because they are identical coloring, just smaller.
Here is the one I had many years ago... she ended up constructing a tunnel the entire length of the 20g long from one end to the other.
That video is hilarious! It’s like a Charlie Chaplin film.