The biggest issue for me on full loads isn't the temp difference by adding more, it tends to even out.
It's airflow. You'll want to look the smoker after you load it and try to make sure that air gets to all sides. Smoke flow is the reason.
Some flip, some don't.
Typically the bottom rack, the top rack and the back left corners are the hot spots.
I don't put the small ones on the bottom, I put the large ones (air flow permitting) so they'll get a little more direct heat.
On the bottom shelf, I put fat cap down.