Welcome to the forum. I havnt seen any giant chicken video. The Brahmas I had wernt giants, just standard Light Brahmas and they are good sized birds, until you see them in full molt. Mine were friendly and the older hen would let me pick her up. She was protective of the other hen. Both became broody after the other. I put eggs under one of them and she hatched 3 out of 6 eggs. Their egg production is good.
Adult Brahmas lay large size eggs.
Dual purpose chickens could be any common standard size breed; Plymouth Rocks, Rhode Island Reds, Black Australorps, Orpingtons, Wyandotte's etc...even Sex Links as well as barnyard mixes.
For egg production it's White Leghorns and Sex Links.
I prefer Barred Rocks; steady, reliable, excellent large egg layers for the long haul.