"C2" is actually the wrong term for what it does, with the next update it will be changed to "Lock." This keeps both handles of the bezier an equal distance from the bezier position.
"RelRoll" stands for Relative Roll. This means that the roll is relative to the last roll value. So if you have a bezier with a roll of 45 degrees, and the next bezier is also 45 degree but has RelRoll on, the roll will be 90 degrees at the second bezier.
"ConRoll" stands for Continuous Roll. This is a little hard to explain. What it does is calculates the roll values for the previous bezier, current bezier and next bezier. The roll is then "softened" so that a continuous roll from the previous to the next bezier is acheived.
- Tia