Laura,
About the Inner Post: I get the same behavior with the "Built-In Post" Inner Post: the Pens specified do not have an affect on the 2D Representation of Inner Posts. However, using the "Railing Post 21" GDL Object I managed to get the desired 2D look.
I will report this as a bug to GRAPHISOFT.
About the Break Line:
In the Railing Setting Dialog, select Railing in the left tree structure, then go to the Break Mark Settings panel on the right.
The Lower Break Mark Pen and Upper Break Mark Pen parameters are the ones controlling the 2D of this part of the Railing Floor Plan Symbol.
Loving Archicad since 1995 - Find Archicad Tips at x.com/laszlonagy
AMD Ryzen9 5900X CPU, 64 GB RAM 3600 MHz, Nvidia GTX 1060 6GB, 500 GB NVMe SSD
2x28" (2560x1440), Windows 10 PRO ENG, Ac20-Ac28