Apologies for the late response, it's been one of those weeks!
My thanks to Eric, Jb and Tim who were all very forthcoming with an explanation! It's great to get a response from PTC and know that they monitor these forums
I don't know exactly how the angle will show up, but if you "modify" the Style feature it should show you where it is measuring the angle. That is what clicking that little check mark does. I think that how that angle is measured really depends on how you set up the curve.
It is the angle with respect to the Horizontal Axis of the Datum Plane (DTM4) in your case. (since you are using a planar curve)
In case of Free curves, the elevation is active. In such a case it denotes the elevation angle of the curve tangent with respect to the reference Datum Plane.
The 2 angle parameters are measured relative to the reference plane in the dialog. 'Angle' is measured in the plane relative to the Horiz direction (note the H/V marker on the plane). The 'elevation' is measured from the plane, assuming the tangent handle is not parallel to the plane.
To select a new reference plane, click in the Plane collector and select your new plane reference.
Hope this helps
And again from Tim...
As for the 2nd part of your question, does the attached help?
The 2 straight curves are my construction geom, and from these I build an internal datum plane (all inside Style). Now I can reference the end angles of the curved curve to this new plane, and therefore make them equal. Is this what you're after?
I've uploaded his attached part to a shared folder for all who are interested! Very nice tip! Works great! Just click on the link and then select the free option and you will be given a download option!