Particular care needs to be taken for the shoulder joint, unlike humans that have a ball and socket joint, the dog's shoulder is held together by muscle and connective tissue. Think about it - the dog is landing on it's front legs!
Human shoulders and canine shoulders (along the lines of the scapula and humorous anyway) are VERY similar. Neither has a very pronounced "socket" (like a femur in the pelvis). BOTH are held together w/muscle mass and connetive tissue, but BOTH rely on the head of the humorous to be able to rotate on cartilage between the the bone and scapula.
Now if you want to talk about how the scapula connects to the rest of the body, THAT is very different in bipeds vs quadrupeds. The scapula in quadrupeds is connected ONLY w/muscle and tissue, where as in bipeds the scapula is virtually a part of the clavical which is then connected to the top of the sternum, or more specifcially the manubrium. While the scapulas themselves to "float" over the back of your ribs, the whole structure is better supported by being connected to other bones.
This is a dog skeleton I put together...the front legs are ONLY connected to the skeleton by a thin wire I run from the ribs to the scapula. I usually take a ball point pen, empty ink cartridge (that thin straw inside) and cut it about 1/4" long and use those to but the appropriate distance in between the scapula and the ribs; to properly simulate muscle buffers.
As for OVERS vs. VAULTING...that's everyone's choice. Level of difficulty does increase for vaults rather then over's though. Of course, it's good to start w/basic over's. You can do "easier" vaults (leg vaults) w/out much height. You can do back vaults w/you kneeling on the ground. The dog will jump as high as you place the disc....most of the awesome dogs I saw in Indy were jumping NO HIGHER on ANY vault then what they'd do to simply jump up and catch the disc out of the air, or doing a flip catch. There were awesome handlers who could place that disc well. Disc placement IS what ti comes down to in vaults.