How to Fix the Funky Movement in this game
Go into options and change Controller Left Stick deadzone settings to 99, 30, and 100.
No more forward walking speed getting cut in half and it helps add a little bit of weight to player movements, which I like.
I play on PC with a keyboard and mouse so it's weird that controller deadzones are affecting my keyboard movements, but it's also weird right stick deadzones are affecting my mouse aim...
I brought this up to DICE's lead controls engineer back during BF1 and he shot me down saying the code paths for mouse and gamepads are different. Years later he clarified his stance by adding this.
At least that was the case when he wrote the code for BF4, and perhaps the Frostbite engineers changed something when the game engine was upgraded to Frostbite 3 for BF1.
So yeah, both keyboard and mouse inputs are affected by controller deadzone and acceleration settings. I'm still experimenting with the best mouse settings. So far they all feel pretty bad. It's like there's acceleration for small movements but trying to do big movements like a 180° spin causes deceleration and you only do a 90° spin instead.