Here is my photography cheating scale for rating what's cheating and what's not:
Level 0. No cheating.
Applying modifications that affect the entire photo.
Basically, most of the things that can be done on Lightroom. This is not considered cheating. Eg. Modifying white balance, color tone, exposure. shadows, highlights...
Level 1. Basic cheating.
Editing elements of the photo.
E.g. The photo has the moon in the background and you make it bigger.
Level 2. Medium cheating.
Editing the elements of the photo by obtaining material from another photo that you took at the same time.
E.g. In the background there is a bird flying and you add another one from another picture that you took at the same moment.
Level 3. Extreme cheating.
Editing the elements of the photo by obtaining material from a photo of another person (the internet).
E.g. You change the sky in your photo for other one from the internet.
How much of a cheater are you?