Alright here we go:
Forward walk tier list:
S tier- Kotal Kahn
A Tier- Liu, Kano, Kung Jin, Jacqui, Cassie, Takeda, Sub Zero, Kitana, Jax
B Tier- Quan, Raiden, Ermac, Erron, Mileena, Scorpion, Kenshi, Goro, Reptile, Sonya, Ferra Torr, Shinnok, Dvorah
F Tier- Kung Lao
Back walk tier list:
S Tier- Kitana, Jacqui, Liu Kang, Johnny
A tier- everyone else but Ermac
F tier- Ermac
As far as runs go they are pretty much all similar except that Goro, Ferra torr and Jason have significantly slower run speeds.