My base version, for all physics settings, was all done in 2018.2.0b11. My character controller and his responses throughout the world are entirely physical. Just about the entire world is 2D physics. I'm not sure if this is me... But it feels just a little crisper in 2018.3, a little less plasticky, or something like that. It all just feels ever so slightly different... but I can't quite put a finger on what that difference is. There's no other differences between the projects other than the version of Unity they're running in.