If you want smooth animations regardless of game speed I would highly suggest using other means than frame animations.
Spriter, Spine, or animate parts of your characters with code or timeline feature. As the inbetween frames are calculated in realtime based on curves rather than frame-by frame that is slowed down.
Of you take a 30fps frame animation and play it at slowmo (10% speed) it will be a view as 3fps animation, and will look like the frames are choppy.
Timeline based animations will calculate the inbetween frames regardles of speed so will always play at framerate.