Well there, Special C
I defer to your experience in Motion, since mine is quite limited (about a week now). However, I’m pretty adept at AE, and am very comfortable with the idea of layers, and precomps, and I’m pretty sure I get the idea of objects within layers in Motion, and how that’s similar to a precomp in AE.
However, to be very specific, the filter Simple Border still appears to me not to respect masks not matter how you embed them. I’ll reread your posts a few more times and retry, but so far, it’s raster only.