I have owned six. Happy was from a puppymill. Kota was a rescue who was found wandering the streets eating trash so no idea where he came from. Auggie, Pepper, Payton, and Georgie are all breeder dogs from lines that are Ch and working (all but Payton grew up on a farm with sheep out their window.) but skew heavily working. My current crew are admittedly not typical because they are bred to be working dogs, so my answers are going to be somewhat skewed.
What is their drive like?
This is a tough question because the definition of drive varies by person, but with my definition... Happy and Kota were not really drivey dogs. They were adaptable, thrilled to go for walks and run and play in the backyard but neither were really much for long hikes - and they were quite pleased to do nothing all day ever. For the majority of their life they were in an apartment with no yard or a townhouse with a postage stamp that was called a yard.
The rest are varying degrees.
Pepper is what you might call a joiner. I don't see a lot of drive in her by herself, but she loves to run with the rest; if the other three are chasing down a rabbit, say, she will go after them to join in the fun.
Georgie is pretty drivey but her personality is also soft. She can be upset easily and change her mind about doing something if her feelings get hurt; I don't think she would make a good sheepdog for that reason. I think she is more likely to lose interest and leave if a sheep tries to stare her down than to return the stare and turn it. She is what some people might call busy but not a constant go-er, nor does she really suffer if she doesn't have much to do.
Auggie is also fairly drivey and has a harder temperament. He is resilient. That said, he is also adaptable, and while he would much prefer to be running around getting plenty of exercise, he is also happy to spend a lot of time just chasing a ball in the house. He will get bored and destructive if not occupied, but it's not a dire situation with him.
Payton has the most drive and is a lot of dog. He did not come with a hard temperament but I've really worked hard to get his personality tougher and rougher and more bounce-back-able and I think I've succeeded based on the changes in the dog and comments bystanders have given me on him. He has not been on sheep yet so I can't for sure judge yet but no lack of drive on this dog. He really needs some kind of mental stimulation (physical is okay but it's really about working his brain) or he is bored and becomes very... um... annoying to live with.
How "trainable" are they?
It depends on the dog of course, but all of them were relatively easy to train and good to pick up on tricks.
How "Velcro" are they?
This again depends on the dog and also depends on your definition of velcro. Pepper is a wants-to-be-touching-you-always kind of dog, actually more of a wants-to-be-one-with-you kind of dog. Neither Happy nor Kota really cared that much about making sure they knew where you were or had to be touching you or anything. Auggie likes to know where you are but doesn't necessarily need to be in the same room, although when he was younger he definitely liked to stay in the room with somebody - he would alternate between being in a room with my parents and then make sure I was still where I was and hang out with me, then go back to check on my parents, repeat. He may or may not follow me if I get up and leave the room - he might wait to see if I come back and eventually follow if I don't. Georgie is pretty much like that. Unless Payton is running around playing, he will not let me out of a general line of sight - he doesn't want me to get up and leave the room without him. He wants to follow me from room to room.
Usually, how are they with other animals? Do they have a tendency for DA, or DR?
DA and DR aren't typical. Auggie was raised around farm cats so he thinks they're something to play with. Payton wasn't and I don't think he sees them as something to go after, but I worry that if my neighbour's cats ever come into the yard and then take off or something, he might chase it, and if he catches it... I don't think it would be good. Auggie and Payton both have nabbed squirrels and rabbits, Auggie has nabbed birds. Auggie has never bitten or tried to grab wool while herding, not sure about P because he hasn't been on sheep yet.
What is their overall temperament like?
This is a tough one to answer because I think there's a typical temperament and then there's the working temperament which I have in Auggie, Payton, and Georgie, and then there's Pepper who is the oddball of course. I agree that generally speaking they are easy to live with dogs. I don't overall think they need "jobs" - Kota and Happy certainly didn't and Pepper doesn't. The sport dogs obviously love their sport and love to play, Payton loves DOING in general, but I think Georgie would be fine without a "job" and Auggie is super adaptable in general, he has transitioned well to not doing a lot of agility training and very very little trialing. I have known many a sheltie, even sport ones, who would be fine without much to do. A non-working bred sheltie is easily a couch potato dog. Payton's sister, as it happens, is a huge couch potato.
What lines, or breeders per-say should I avoid?
If you ever want to PM me to look into a breeder or ask around about them, I'd be happy to. I have connections in the breed and connections who have connections LOL, so somebody usually knows something about somebody or knows they are somebody not worth knowing shall we say.
What is their "view" on people? What's their reaction when they meet at unknown person?
Laur is correct that "aloof" is the proper temperament - according to the old school breeders that is specifically NOT shy and shyness is actually incorrect - just aloof. Kota fit this perfectly. Content to greet people and have them pet him, but his main concern was really his people. Pepper is terrified of most people. The rest love people. Auggie and Georgie will both tackle a stranger if given the chance, although Auggie is much better now that he is older and basically waits for permission to tackle - which is Payton's trained response, to wait until I give him permission and then he will go greet somebody with enthusiasm. Happy would practically whine himself to death if there was a person looking at him or smiling at him and he couldn't say hi. I would prefer a dog to come with a more aloof temperament, honestly, but I will take the enthusiasm over Pepper's reaction every day of the week.
And, just because... What are three words to describe the breeds overall temperament?
Uhhh... fun... clever... cute? LOL.
I will say barking is just part of the breed. I don't own "trouble barkers" but I know some people who have them. It's just a thing and if you can't stand barking, look elsewhere.