I want to know this cause I want to see how fast it will move and attack, also I think I heard something like it lowers move reduction? !Not mega!
Speed does lower a moves cool down time, but it does NOT affect the rate at which a Pokemon can perform a move or how fast they walk around in Lumiose
for example. Greninja has a base 122 speed stat making it the FASTEST non Mega Evolved Pokemon, but even with a max speed stat of 377, it's moves will still perform in the same time it takes a level 1 Froakie to use moves, but in Greninja's case, that move he used will take a bit less time to recharge
Source-https://www.reddit.com/r/LegendsZA/comments/1ojnwg7/a_quick_speed_breakdown/