You can lean into the turn FARTHER with a windcheetah because of the joystick steering. It's also a bit lower to the ground, which should help. But I've raced on a greenspeed X5 and been able to lean into turns that I would have slowed down for on a two wheeled bike.

I've brought it up on two wheels a bunch at high speed. I don't think you can say that at "x" speed the trike will flip. It depends on which trike, which person, and how far they're leaning.

There are racing trikes - greenspeed x5, catrike speed and 700, windcheetah. All of those will be good. The cheetah is the king though!