[Export FBX - the feet float above origin ]
This is current program status, it is caused for the best mesh symmetrical.
You can see the details from this forum post:
Can you provide the more description about the problem you encountered when the feet float above ground?
[OBJ with current pose]
This export does not have the ability to back to CC, it is not executed the release-HIK rigging.
So you can get the feet keeps original position (not float above the ground)