I’m aware of some stuff like that some instances have defederated from others for anti-communism (lemmy.world / hexbear.net), but that’s where my knowledge ends.
I’m looking to understand what instances to be aware of, each instances’ political leaning, defederation etc.
I’m not sure. You can check their “instances” page if you’re curious. You can also block instances from the web interface, so it doesn’t have to be something you have to remember.