The problem with cutting the edge is the metal won’t be powder coated like the rest of the chassis on the cut… depending on your level of OCD this might be a problem, haha this train of thought might be more of a reflection on me though.
Its a subtle ~1mm offset, but this is what the back of the case I did looks like, which is technically not within ATX specification for the IO cutouts:
This is supposed to be the thread on the case but I need to update it: