Is the first index in a path's vectorPath the start of the path or the first waypoint?

When you get a path returned, is the first index of that path the first waypoint to walk to or is it the starting position?

i.e I am stood at 0,0,0 and want to move to 100,0,100 the starting position would be 0,0,0 the first waypoint would be 1,0,1 (assuming diagonals and node size of 1).

Hi

It depends on the setting in Seeker->StartEndModifier->StartPoint
If it is set to Original, the first element will be the (0,0,0) (the exact point you requested the path for). If it is set to SnapToNode, it will be the first node on your path (most likely the node you are standing on), if it is set to ClosestOnNode, it will be the closest point on the node you are currently standing on (a grid node is handled as a square with a size, it will be the closest point on that square).

In this instance I am just using ABPath or FleePath directly, so I assume it is the starting position?

It will be the first node in the path. To get the original point that you requested the path with, use ABPath.originalStartPoint.