What is the earliest a pup should leave its litter mates. I have been reading up and so far have between 7 and 12 weeks.

It depends on the breed. 7+ weeks is usually fine for the average breed, but some toy breeds are too small and fragile to leave so soon, and need to stay till 12 weeks.

i had my current pup at 6 weeks. It was ALOT of work for me, more than the 7 & 8 weeks pups id had previously, but hes a lovely pup! Also he was coming into a household of 3 other dogs ,so he did have other dogs to interact with & show him how to be a dog. I still dont think i "really" bonded with him till about 16 weeks though