In Photos, image pairs can be JPEG+RAW (using the JPEG as original) or RAW+JPEG (using the RAW as original). My understanding is that while using the JPEG as original, edits in Photos adjust the JPEG, and the RAW is pretty much ignored.
I have noticed that when I open Nitro, JPEG+RAW image pairs are displayed with the RAW filename, even though the JPEG is meant to be the original. It seems like Nitro only ever uses the RAW file as the original. Is that correct?