First and foremost welcome to the threadiverse, the long-form version of the fediverse or simply, the Reddit alternative bka Lemmy.
Disclaimer, I’m very active in this community, so I’m not really the man to do your induction.
What I will tell you though, is that Lemmy is 100% what you make it. My advice to you is to stay away from ALL and also to stay away from Lemmy World. You will eventually find your way to both, but let it be on your terms and not your default interaction. Lemmy World is the biggest instance and so comes with the baggage of a lot of people dying to be heard and accepted by any means possible. ALL is the worst of that. If you stick to the communities you want, you’ll be fine. You’ll quickly notice some of the same names, but they’re all independent. You can be aligned with someone on something one minute and total against them in another topic and that’s healthy.
But as of right now, you’re the coolest person in this thread, so you’ve started well.