Great question, yes always aim low. Deer drop most of the time on the shot. Even if the deer does not drop, because of anatomy all of the vital organs are located in the bottom 2/3 of the animal. The heart is in the bottom 1/3 along with some really big blood vessels that would be great to hit. Ideal shot placement for me on a broadside animal has always been tight up against the front leg in the bottom 1/3 of the animals thoracic cavity. Aiming bottom 1/3 also has the added benefit of allowing you to hit farther forward in the animal and avoiding heavy bone. Because the humerus and scapula of 4 legged animals angle forward and out of the area of the vitals, it gives a nice “vital V” to quote a really annoying guy on YouTube.
You should go check out Ranch fairy on YouTube though, he’s got some great stuff.