Here's a trick for getting some nice PWM from an operator pair on the PreenFM2.
The trick requires a pair of operators so use something like algo12. Turn off all the IM, v and Mix except set Mix1 to 1.00 and IM1 to 4.08
Set Op1 to a Square Wave, keyb Freq 1. Set a no attack, full sustain envelope while you test it out.
Set Op2 to a saw, keyb Freq 1. Again, set a no attack, full sustain envelope.
Now go to the LFO page and set LFO 1 Sin Freq=0.46 Bias=0.5
In the matrix page make sure all 12 Srce are set to none. Then set Matrix 1 Srce to lfo1 Mult=0.9 Dest=IM1
You should have a PWM oscillator sound. LFO1 controls the PWM speed. The amount of IM1 is a bit tricky. If you use too much you get an octave up effect happening.
I've attached a string sound I made using this trick. I used 3 detuned PWM pairs. The filter is mapped to the mod wheel.