Here's what I have learnt about keyword cannibalization (feedback appreciated)

I've been going down the cannibalization rabbit hole lately, and wanted to write up what I've learned so far. This is a mix of things I've tested myself and stuff I picked up from posts here. Happy to be corrected on anything because I'm still figuring a lot of this out. What even is cannibalization? The short version: it's when your own site competes against itself. You have two (or more) pages targeting the same keyword, Google can't decide which