I've only ever had dogs from the SPCA. I found adopting them as youngsters or pups meant their history was clearer. The folks at the SPCA tend to get to know the dogs in their care, and are careful to let you know the history, temperament, etc. They've also all been house-trained at that point. We've had wonderful dogs from there. It's always been a great experience.
I admit to a bias against purebreds. I've yet to find a breed that doesn't have inbred health problems, usually expensive ones. Some are downright neurotic. Getting a reputable breeder is important, but even they have a limited gene pool from which to draw. I also think there is an issue with overbreeding and too many unwanted dogs, so adopting one appeals to me on that front, too.
As for training, I have used gentle methods although judicious use of a proper choke chain can be helpful; if fitted and used correctly it should not cause any pain to the animal. I took a dog training course years ago with one of my dogs when she was a pup and based my training on that. You do need to do "homework" and work with the dog pretty much everyday. But after six months we had a dog who could be taken anywhere and could reliably be worked off leash as well. I am not into crate training, though I know many people favour it. There are many dog-training methods out there and my bent is towards those that work within their nature, are gentle but firm, respectful, etc...no pain or punishment, and also no rewards (like giving food; personally I think those methods are doomed to fail when the dog decides they'd rather run away than have a snack at that moment!).
Dogs need exercise and socialization. The former is critical b/c a dog with too much energy is like a toddler with too much energy: they get into things, destroy things, bark too much etc. It's not enough to just keep them in a yard. They should have one, good long walk a day (if you run or hike, even better), IMO. Alternatively, take them to an off-leash park (when you are confident in their training) and use one of those ball throwers to give them some good exercise when you yourself aren't up to it.
Having a dog-door with access to a fenced yard is also a great idea, so you don't have to worry about coming home to let the dog out.
It's been a few years since I had a dog and I'm really missing one. I've been talking with DH about getting one, but of course we'd need our landlord's permission first. If we get the go ahead I am definitely heading to the SPCA. I prefer medium sized dogs, and while I'm partial to border collie mixes (very smart dogs!) they do require more exercise than more sedentary types. Again, the SPCA would know the energy level of the dog and can advise you accordingly.