2nd picture - that fat will never truly render. most often it is removed when trimming before cooking.
3rd & 4th pictures - looks like the edges crumbled. if so, you overcooked the brisket
Harry Soo and others will use a chunk of smoking wood under their packers if there is a space...
That last statement is so very true. On Saturday mornings, in our walk to the tent, we (wife and myself) avoid traversing near team areas whose pits are shadowed in a cloud of smoke or reeked of burnt oil. Thankfully, there numbers are few....
Were the 2 butts from the same pig ?
Multiple conditions influence the denaturing process of each piece of meat. Even the conditions surrounding the animal just prior to entering the abattoir. So do I find it unusual... No