How much post processing is too much? What is the border?
Different competitions, and different categories of a competition have different rules and parameters of what you can or cannot do with the post-processing, it is complicated, so as a photographer you are going to enter a competition, make sure you read all fine prints of the rules carefully.
Personally, as a professional wildlife photographer, here are the principals of my guide in terms of post processing:
Principles of Professional Post-Processing
The purpose of post-processing of professional nature photography is not creation, it is an enhancing tool to help the photographer to realize the vision when he took the photograph, so enhance, adjust but do not manipulate!
a. Do not add or subtract or relocate the contents of the image, you can crop, but the content of the image must match its RAW file, that’s the bottom line.
b. Do not change the physical characteristic of the image pixel, i.e..
like blur
c. Partial adjustment with clear intentions
d. Enhance the color naturally
e. Do not change the logic of the light