Then you should be able to set up the MoveIt connection in the same way that the sample does with the default robot.
Regarding OMPL, you could try the Python bindings in the Python user programming environment of the IsaacSim application. I’ll ask around to see if anyone here has tried that already.
The ROS moveit connection uses a standard Joint state message which provides the target joint angle for each joint. As long as your planning stack (OMPL or Moveit) can provide that then it will work, there is no moveit specific code in the ROS bridge so it should be flexible.
You can rostopic echo /joint_command with the existing moveit sample to see the commands being sent by moveit to isaac sim.