Are you referring to the Border collie or the Rough/Smooth collie..?
They are two very, very different dogs.
Assuming you mean border collie, I have the working line and I know a few other working line owners.
I personally do not agree with deliberately breeding working dogs into show/pet dogs.
I think in breeding for low drive you lose a lot of the charm and individuality of the breed and I think sometimes you can really muck up stability/nerve as well if you aren’t careful.
For example, I find that in show/pet lines of ‘better’ bred Border collie and German Shepherd (similar, both herding breeds) they tend to be more gregarious/friendly with strangers.
Which is nice, but it’s not really correct for either breed who are typically ‘one family’ dogs and aloof with strangers.
Both breeds are naturally somewhat high strung and in the Shepherd especially, the ‘worse’ bred show/pet lines can be very neurotic and nervous.
It’s a big problem also in Border collies.
In both lines.
Children.
Mine likes children, she is really, really tolerant and sweet and gentle.
However.
They are not a breed I would generally recommend for young children because they are somewhat high strung and like to control.
Generally speaking they like peace, quiet and order.
Some collies get very very stressed by normal, noisy, lively child behaviour and will either try and control them (herd them) or will get upset and hide, get aggressive etc.
It is very important not to tolerate any herding behaviour towards the children, don’t be tricked into thinking a show line automatically won’t have any herding instinct.
Some are very low drive indeed, some or not.
Herding instinct generally, is present from about 8 weeks.
Affection.
I don’t find them overly affectionate truthfully.
Mine loves a hug, she will come and press herself into you but I find that she far prefers to play than cuddle.
Generally, she’ll come up to me a few times a day for a brief kiss and cuddle then she’ll bounce off to find a toy.
She is supremely lazy in the house and will snuggle into you if you sit next to her while she’s resting but rarely approaches herself.
When DD was small we would regularly wake up in the morning to find that she’d snuck out of her in the bed and she would be snuggled up with the dog.
The ‘off switch’ is partly down to training and partly genetic.
You need to spend time with the prospective pup’s parents, that is the best indication of what your puppy will mature into.
Nervy, neurotic parents are highly likely to produce nervy, neurotic pups regardless of how you raise it.