A few items from my POV
1) Engine fires in small ac are rare and usually go out as soon as the engine is shut down. This was the case in the two I have personal knowledge of ( C421 and Islander).
2) I have been instructing full and part time for 16 years. My club has a policy of annual recurrent training. I have NEVER had a PPL conduct a satisfactory forced approach on the first try during a annual check ride. Many in my opinion were so bad they stood a good chance of killing themselves. Therefore I strongly believe PPL's should practice this manoever regularly, it may save their life.
3) When instructing PFL's I used to initiate the engine failure by pulling the mixture to ICO. One day in a c 152 , after 6 full PFL,s we returned to our home airport, landed and pulled into our parking spot. The student pulled the mixture out only about 3 feet of cable came out as the engine died
So I now initiate PFL's by pulling back the throttle...