There is no need to change the service while driving.
Simply decide what mode want to use before go out.
Does anyone change the map provider while driving?
Automatic rerouting remains automatic.
If want manual rerouting, can disable it.
If want forced offline routing, can select it.
Can check it in the two announcements and its own topic:
What offline maps? Offline maps are for view maps.
Each offline router requires its own routing data set.
None app is perfect! 
Like mentioned too many times, we start with simple things.
If someone doesn’t like how a feature work, is free to skip it.
Or wait patiently for future improvements, cannot satisfy all!