Mechanically, with a shirt, I think that having the weight, wrists and elbows in line is optimal because, think about it, shirts are helping out to raise the humerus, but don't help the triceps.
If you bring the elbows back slightly, what it does is shorten the lever at the humerus. If your humerus is 12 inches long, and you can come back 2 inches with the upper arm then the lever at the humerus drops from 12 to 10, allowing 12/10s as much load (ie, more). Also if it didn't change your touch point, the humerus would even have a higher angle above parallel (which also lowers the lever length, which is the horizontal distance from the vertical line of the load, and the shoulder).
The problem is that most people will get a lower touch point and therefore a "more bent" elbow as they touch higher on the chest.
Ideally, the balance in strength between the triceps and the muscles that extend the humerus should determine how far back to take it, and for most people this ends up being "not much".
Ed Coan discusses touching higher with raw pressing.
But all in all, in reality just a very slight bending of the elbows will create the optimal raw pressing position.