So I think a lot of people are commenting based on what they've read about ACDs. I don't know that many actual ACD owners have responded. You may want to ask around r/australiancattledog

I have an ACD. He's amazing, calm, and well-behaved. The first year was tough. Very tough. It took a lot of patience and commitment to overcome his separation anxiety and to put an end to his nipping. It's not impossible, and if you don't lose your patience and give up, it's really not even that hard. It's just a slow process.

These are smart working dogs. Most, though admittedly not all, want to obey and learn. If you're willing to put in the time you can train yours not to nip.

You absolutely need to provide frequent exercise. But multiple hours every day, come hell or high water? Not really. My dog doesn't like being in the rain. He's totally content to laze it up on the couch with me until the sun comes out again.

Are they great around kids? Not inherently. It will take a lot of training and supervision before your dog is kid friendly. Again, smart and obedient by nature, your dog will learn if you put in the time.

ACDs are not great beginners dogs if you're not 100% positive that you want to put in the time and energy. If there's a chance you're going to get frustrated and give up on training, forget it. Get a calmer and more subdued breed.

If you know you want to train your pup, and if you're going to treat your ACD as a member of the family rather than just a pet, they're really not so bad for a starter dog. They will learn easily if you will teach.

Good luck.