@Anonymous
Boundary Lines
You already stated the reason... you cannot edit boundary lines because they reside IN the family! If you place a symbolic line in a Family...Can you edit and/or control that Linework in the model through the family properties?! No, you have to edit the family and create another line
Transparency
It seems like your question came up because you wanted to do something and the Filled Region did not achieve it. Filled regions as a family are treated as Annotations hence in the family they have only the option to be either Opaque/Masking or non-masking.
- Once you place them in the project you can override their visibility (by element or category) and apply Transparency as you wish...similar to any other family in principle
- you can even override the original Fill patterns by applying Surface Patterns and have a 2 in 1 filled region; however, surface overrides should not be abused as it may affect visibility/graphics of other components in views as well as printout)
