I feel Fusions spline tool is a blessing and a curse in the same time 😉
While easy of use is fantastic the UI or G1 G2 options seem to be very hard to understand and need some improvement
to make sense.
For example Alias has very striaght forward G0 G1 G2 G3 align tools via the CVs and UI elements:

Fusion with offering spline hanles (tangent and curvature) and in addition G1 and G2 constraint is honestly hard for me to grasp to see what is where going on or how each influences whom. This might be another example for what we seriously should have a CV curve like Inventor as well.
Here is a video explaining my understanding issues:
https://drive.google.com/open?id=0Byzv_NlyKp_2MnR6b3diREo4bVU&authuser=0