Yeah, that’s possible. You can create a totally private instance (where nobody who’s not a member can even see posts), or just an independent instance that isn’t federated with anyone. I personally don’t know anything else - I’m just paraphrasing someone more knowledgeable.

As for Beehaw, it’s the instance I use most. When they defederated, the mods gave trolls as the biggest reason (they are very transparent about their decision making, which I appreciate). They were simply overwhelmed with mod duties. There weren’t a lot of people running Beehaw (I don’t know if that’s changed in the last few weeks), and they defederated from the instances that most of the moderating workload came from. They said that defederating was a last resort, and hoped they’d be able to re-federate some day. We’ll see.

They are very serious about maintaining a civil atmosphere, but they’re not “word police”. Disagreements are fine as long as you’re not a dick about it. It’s not about what you say, so much as how you say it. If you’re not a rude, nasty person, it feels like any other instance. I’d recommend giving it a try!