It's been a few years since I used Fusion 360 lathe. It does provide good code for use by Mach3.
If my memory is correct, from one of the pull downs you can access / download load different post processors.
Just for reference you may find the CPS in the following directory of your PC:
C:\Users\user\AppData\Local\Autodesk\webdeploy\production\890691bd91ea0296c1b94572fdc7dda4ba2e48f0\Applications\CAM360\Data\Posts
You can edit them to customise, BUT, you better know what your doing. There was a video on how to edit them, about 1 hour long, that I watched and educated me on how to make changes.
Have Fun,
RICH