After much torment, the solution is simple: Don't export FBX from Blender, use GLTF from Blender and then FBX from Casc(cause s&box won't use GLTF). Here's the workflow:
Click the Blender Scene properties tab, and set the unit scale to 0.01 to match with Cascadeur (important for scale)....Your model *may* end up 100x too large from this step as well, so try exporting a basic GLTF format Cube to Cascadeur to test the scale)
Blender character modeling and armature assignments (make sure Armature and Mesh are both Applied All Transforms before parenting/ weight painting so they are both 1x).. (Bonus: Not sure if this is needed, but in Object Properties tab on the Armature and Mesh(both separately), under Relations I set Tracking Axis to +X to match with S&box's Forward since Cascadeur copies the Hips axis on import by default, and +Y is up, to prevent any unnecessary flipping of the model itself.)
Blender Export *AS GLTF* format
Cascadeur import *GLTF*
*FROM CASCADEUR* export your model as FBX with Y-up, and also your animations as FBX Y-up.
????
Profit
All animations and models are correctly oriented upon S&box import.
