I’d like to make my most-perfect Legendaries into the strongest attacker possible, using Elite TM if needed. Regigigas shows Normal-Type Hidden Power as the best fast move. Repeated use of Fast TM switched back to Dragon Type Hidden Power every time, and the Elite Fast TM did not show a choice of which type, either.
Question 1: How significant is the typing for the effectiveness of Hidden Power?
Question 2: Is there any way for me to choose which type of Hidden Power?