I'm the developer - feel free to ask any questions you might have. There are a couple of threads about Floppy Emu already in the hacks forum.

Emulation works for 400K, 800K, or 1.4MB disk images with Macs from the original 128K to the Power Mac series. I haven't looked into the HD20 emulation yet that uniserver mentioned, but it should be theoretically possible since it uses the same interface.