Are ffmpeg prores files reliable enough to be used in production/broadcast environment?
I've had no problems producing prores 422 HQ .mov files with ffmpeg on my Windows machine for Mac-encumbered clients, including delivery to TV Networks for broadcast. I have had some problems with prores 4444 but only when the files have alpha channels, however that bug seems to have been fixed recently.

I don't know if anyone has done any head to head tests with the results you get out of ffmpeg vs a native apple app or something like adobe media encoder. That would certainly be worth doing.