Alright, so I was 100% wrong on the Q (just to call myself out and clear up bad info).
The Q400, if you select the condition levers to below 850 in flight, you'll get a PEC caution and the prop will go max RPM's and be stuck there. The big thing is not going below flight idle on landing (cause they will feather). Not sure what the ATR does/will do.
I went back in my notes of things that happened back in the day (not to me, this was another crew out of MFR in the morning). We had a crew takeoff early morning (it was 5am something, MFR-PDX according to my notes) and they selected the condition levers below 850. Dual PEC caution, ran checklist and returned to MFR. During landing, the pilot's went below flight idle and both props feathered. Aircraft stuck on runway/runway closed.
Granted, it's been 3 years, 2 different airplanes and a different airline ago, but going to give myself grief on not remembering this.