Falling through the floor is most likely a problem of your root position (X=0, Y=0, Z=0 in local space of the prefab) not being at the bottom. That's what'll be placed at spawn points.
You can solve that by defining the Spawn Offset in the combatant's settings.
When using Mecanim and a Character Controller (e.g. required for the built-in controls), you need to disable Apply Root Motion on the Animator. Also, try enabling Use Position Change in the combatant's Movement Settings. And make sure you have Use Auto Animation enabled in the combatant's settings if you want ORK to handle the movement animations :)
If that doesn't solve it, I'll need more infos on your setup.