This appears to be an issue with the weights/priority of the animations, rather than the speed. I’m not that well experienced with animating, but this fact should help narrow your issue down.
it could also be a problem with how you handle the animation since if you’re using the default animation their weights and priority would be the same as the player ( I think )
the animator is already doing heavy work for us on the player, so duplicating it might cause a slight delay instead of duplicating it, you could modify the original to target two humanoids, or Leverage Animation Data with GetPlayingAnimationTracks()