Many double-neck pedal steels include both, with a C6 neck alongside the E9.
For most players, E9 is more straightforward to start with. C6 focuses more on chord structure and gives you extended chords and richer harmonic movement, which can take time to get comfortable with.
Pedal steel tunings don't stay fixed. The base tuning stays the same, but pedals and knee levers constantly change the pitch of individual strings.