I export them in .ase
I've recently noticed that the fbx format exports the smoothing groups as well which is good but unfortunately useless when I'm to import a second uv channel.
Let me explain:
When I export a mesh to game studio I export a part 1 which is formed by mesh + textures, and a part 2.
I use the part 2 to extract the second uv set with baked shadowmap.

If I use the ase format everything works fine.

If I use the fbx format it doesn't because it re-arranges the vertexes index differently or whatever, anyway it doesn't work.

As for the soft hard edges what do you mean? antialiasing?