I would appreciate comments from the experts on the subject matter on the readings I collected and posted below to see if those are within acceptable parameters:

I was registering quite low voltages at idle w/ an OEM alternator (105 amps) so after I installed TFF-7861CBULL6G (160 amps-single wire, I was surprised to see that, although slightly better (about half-volt at idle), the problem continued. So the internal regulator being faulty was highly unlikely to be the perpetrator since both alternators caused the identical problem. After further researching the probable causes on posts, I went to work to eliminate everything that may be the culprit other than the alternator & the battery: Cleaned ground contact points, starter connection, added a single 4-gauge wire directly to the positive terminal of the battery, cleaned the battery connections and ran extra ground lines separately from the negative battery connection as well as one from the alternator ground screw to the chassis

Below are my results to serve as a guideline; ALL readings (volts) were cross-checked with a voltmeter at the battery contact points which almost exactly coincided with the gauge readings therefore effectively annulling any possibility of an improperly functioning gauge. Also, each auxillary was engaged on top of the previous one during the test:

Engine OFF: 12.28 (no battery recharging is performed prior to test)

1) On IDLE:
No aux: 14.27
Low-beam: 14.12
Fog lights: 13.50
Hi-Beam:13.33
A/C:12.40
Rear Window resistance: 11.77
Lighter: 11.58
Brake pedal depressed: 11.29

2) @ 2K RPM (stationary)
No aux: 14.31
Low-beam: 14.72
Fog lights: 14.70
Hi-Beam:14.41
A/C:14.30
Rear Window resistance: 13.92
Lighter: 13.90
Brake pedal depressed: 13.68

3) After driving for 10 minutes w/ ALL AUX ON, on idle w/ brake pedal depressed (these are close approximations as the reading are done from the gauge):
No aux: 12.2
Low-beam: 12.2
Fog lights: 12.0
Hi-Beam:11.9
A/C:11.8
Rear Window resistance: 11.3
Lighter: 11.0