Slipstream can now be set to either "weak" or "strong". "Strong" makes the slipstream as strong as before, while "weak" weakens the slipstream effect considerably. Possibly my favorite thing about the 2.0 update along with being able to adjust pp in shuffle.
He said offline.
No adjustments possible in A-Spec races, but in arcade and practice.
This.It can only be changed online as far as I can tell. PD in their infinite wisdom must think we don't need or want it offline.