3) Took one sub out of config 2, so the amp was still bridged, but it
was only running into 1 sub, and it saw a 4 ohm load. This setup was
equally as loud as config 1, though not as loud as config 2. But the amp
obviously ran a lot cooler than config 2 and I imagine the amp would
last longer.


You ran one sub in a box twice as large as it should have been? That's not
a fair comparison.