Importing a Blender rig into studio with proper joint orientation and mesh boundary box

If I just simply export the rig into Blender right now the local transformation of each motor6D is not properly set

This is the intended behavior of the local transformation of the joints

This is how it behaves in studio when I do the same local transformation

Additionally the boundary boxes of the meshes are completely different as well, I want to make it so a mesh with the same shape has the same size, different orientation, currently it gives me a rig with meshes with different size and same orientation

This tutorial worked for me using the deformation effect so had to import the custom rig and mesh from Blender. But I don’t know if it will work for you since it seems that the bones from your example move in a sort of domino-effect way, but anyway, here it is:
(6) Roblox SkinnedMeshes/Deformation Tutorial - YouTube