Ok, so, there is no way that you can write out HFS disks from the Finder from your modern iMac to the floppy.
However...
There may be some command line-based tools to allow you to do this. You can possibly write out an image file directly to the disk, bypassing the Finder and mounting process. I'll see if
@Phipli can chime in here, as he seems to have a good handle on this sort of thing.
As for the PC disk thing, it should be possible to use PC disks on the CC if the appropriate System software is installed. What system does the CC have on it right now?