Well, I am in the “what an incredible job” camp, and am of the “I hope I can do that well” sentiment. My congrats to the pilots at this point.
I have no insight beyond this thread information and have only a few hours 139 to try and comprehend this. However, I am concerned by so many concentrating on the crew before tech details are fully revealed. So far, it sounds like they suffered a cockpit fire resulting in a possible total electrics failure that also removed engine governing where, by design, they freeze until manual mode is selected. only manual mode selection may not have been an option due the electrics failure. So they may have had a double frozen governor with no cockpit indications at all and trying to descend by judging RRPM by sound and feel using the only control they had left. In a smoking cockpit. Maybe.
And they landed safely. Respect.
PS: In my limited experience of the 139, despite the questions and inferences raised above, the 139 ECL do not control engines when in automatic unlike some older acft,,,other than provide a fuel shutoff capability as JGtn points out. You must select manual mode first, and you must have electrical power to do so. As mentioned, it would be a damn sight easier to run through which of the same shaped and positioned electrical switches I could play with from the comfort of my couch as opposed to in a burning cockpit.
and yes, i acknowledge this is also ill informed speculation, but to me it currently suggests a “bravo” is due.