I can tell you about Rottweilers, mine is a puppy still really, but I did a lot of research and he's fairly typical from what I've read. (give or take individual differences in intelligence and personality obviously).
He's massively trainable, I can teach him a new command in about 20 minutes, but he has absolutely no common sense whatsoever and often does things like walk into walls because he's just not paying attention.
He's also massively stubborn and pigheaded, so stopping him doing something he wants to do is much much harder than teaching him to do something.
He's huge and clumsy, so they're sometimes not reccomended for small children - he adores children, they're the most exciting people ever, but it's very easy for him to knock them over just trying to say hello.
He's very affectionate with people he knows and can be a bit clingy with me - they don't do well being left alone a lot and as adults can be a bit aloof with strangers.
They also get bored easily, so lots of training is good for them - I did have vague plans about agility, but he has elbow dysplasia.
He was really really bitey as a tiny puppy and he's still chewing everything he finds.
They also are prone to same sex aggression as adults - so lots of socialisation is important, but mine is well into his teenage stage and no issues with other dogs yet (well except trying to play with dogs that are way too small because he's no idea that he's huge).
He's very full on with everything he does, so masses of enthusiasm and energy, but again, he's a puppy, lol.
There's nothing about them that makes them inherently unsuitable as family pets, they're not really couch potato dogs, but then neither are huskies, lol.