Unfortunately you only get a good overview by being here a long time and paying a bit of attention to the seasonal drama. The biggest pointers, to my knowledge, would be that a lot of instances are defederated with lemmygrad and hexbear (but not all), because otherwise the bad faith campism and trolling gets unbearable, world is defederated with the piracy instance, and virtually every large server is defederated with "free speech absolutists" who let their instances fester with far right types.