Hi René,
The Angle goal is calculated using the approach described in:
https://www.researchgate.net/publication/223069750_Tensegrity_spline_beam_and_grid_shell_structures
With the ‘Strength’ input taken as the value of EI. For units you just have to be consistent across all the goals you use (such as when calculating EA/L for the strength of the Length goal). So generally I use metres, pascals, newtons.
You can read the code which runs inside the component here: https://github.com/Dan-Piker/K2Goals/blob/master/Angle.cs
(Actually the code is slightly different to this in the latest release to improve stability and convergence, but the general approach remains the same, and it converges to the same result)