Yes.
Yes.
The Hellcat's output was dialed back for practical reasons and because it already has more power than you can use below 70mph. The supercharger can move much more air and the engine assembly was tested to about 850hp. If you can unlock the ECU or bypass it with a full ECU replacement, you could change the SC and crank pulleys and gain about 150hp. After that it might not pass a 300 hour dyno test, but you wouldn't reach 300 hours of full throttle even if you went to the drag strip every Sunday for 20 years.
Better way to look ot the Hellcat is as a movie character. The engine is an air-breathing, rumbling, shaking, thing like a monster released from a radioactive cave. The cars are ordinary, but nuts via an injection of experimental chemicals (OK, it's just more air). Heck it even breathes through a hole it it's eye ...as if they tried to kill it but it wouldn't die! The thing just about leapt out of a comic book.
Electric motors are efficient and, uh, they're efficient. While making a slight RC toy sound.
The vehicle it's in can't put all that power to the ground, but you can drive them just like a normal car and service them with common tools any Dodge dealer yet they're 200mph rockets.