I can only talk about mine. He's a complete wuss. He never flares and he's generally very skittish. He runs from a reflection of himself and hides in the back of the tank. He'll stress stripe over the littlest thing but he loses them pretty quickly. Also, he's the healthiest Betta I've had. He's never had a fin rip or any health problem. His finnage is perfect.
The 'wuss' exception is feeding time. He's an AMAZING jumper and he'll dolphin leap out of the water at my hand even when I'm cleaning the tank. He scares me with his jumping. He's easily cleared the tank by several inches, one time landing on the rim and sliding back into the tank (he got all stripey over that too.) A lid with NO gaps is essential.
I've never tried him with anyone else. I toyed with the idea of adding him to my 16 but he's SO big I was afraid that if he DID end up being aggressive towards a cory, that he'd easily kill one. I wasn't willing to take that chance.
I'm not sure about their lineage. I've read that they're a half giant plakat. I've read that they're a breed called Chupang Raja which means King betta in Indonesian.
Here's a Kilo video so you can see what a scaredy cat he is. :P