So in terms of beehaw vs lemmy.world I would be on instance 3 - I can see and participate both, their defederation from each other doesn't affect you, it only affects the users of beehaw or Lemmy.world

This aspect is really crucial for people to understand, so I wanted to emphasize it. This is what gives the Fediverse it's hyper free nature, where if you don't like which instances your instance has chosen tp block, you can always switch to a third instance and have access to both your old instance (thus solving the network effect) and the new one (thus giving you freedom of association). This sort of connected-by-default design choice (I.e. using blacklists instead of whitelists) is also crucial for maintaining the general interconnectivity of the network thats crucial to its functioning.