I supose the tube drive is responsible for the insane piro speeds in the first video...
Not at all. It's all about TR blade pitch and RPM. My TRex 450S can piro every bit as fast as that even though it's a belt drive. I set up a rate switch to turn the ability on or off during the flight. The hard part is keeping the battery in place. Three velcro straps and 2 rubber bands aren't always enough, LOL.