Well, as far as the importance of canopic jars to the pharaoh himself, there wasn't much of a real tie. It was more of the man and what part of him he would leave behind in the mortal realm, as his ka went to the underworld to be met by Anubis' judgement. The sons of Horus guarded the parts you left behind. Imsety protected the liver, Hapy the lungs, Duamutef the stomache, and Qebehseneuf protected your intestines. Although, Tutankhaten's canopic jars were humanoid, which is ... quite odd.
Early canopic containers were actually just chests, or jars. They were later changed to fit with Kemetic religion, and the four sons of Horus took place. Though the jars have changed with time, in most instances, the jars have been grouped into one canopic chest. This usually had a protective spell written on the outer portion of it, to save your body parts from ill will.
By some strange turn of events, instead of using the image of an animal-like god or goddess, in the 20th dynasty, images of humanoid figures were used, much like Tutankhaten's case.
I'm sorry, but I don't know what I could to do help with "where" exactly they were found. If you need a reference for bibliography, I just read through this
quickly, and pieced in from what I already knew. I hope someone can help you with what I could not, and good luck!