The FM engine is almost the same as the preenfm2.
What you get with the preenfm3 is :
. More voices with effect per voice.
. higher sample rate (48Khz vs 42)
. 6 instruments (instead of 4)
. A “mixer” section to have more control on each instrument
. 6 audio outputs instruments can be routed to
. A graphical user interface
. A builtin small sequencer