#1 - About half the Archers I see are wearing Padded Leather for armor... why is that?
Pure coincidence. Because this armor isn't better for archer than any armor between Padded Armor and Lamellar Vests. (dont mind fancy stuff like bride dress ofcourse).
#2 - I see a decent amount of archers, in very light-cloth armor... yet they are wearing mail mittens. I know the penalty for wearing gloves is steeper. So why are they wearing any gloves at all, much less mail mittens? Are they just new players, or am I missing something?
It's just min-maxing. Since penalty for hand armor = effective weight of hand armor *2, with mail mittens you can receive more defence for less penalty than with just heavier armor. Especially with loomed mail mittens.
Main point for armor efficiency - you must have enough armor to survive arbalest bolt but still have minimum penalty for your WPF. So, you need at least 38-42 body armor with minimum possible weight.
Well, some people also use armors to blend at some maps.
Example Byrnie - body armor 36, weight: 8.6
Mail gauntlets - bosy armor 5, weight: 0,5*2=1
Overall armor and weight - 41 and 9,6
Overall armor rating for armor with weight 9,6 = 37
Yes, combo armor+mittens cost little more, but this is not a big money.
See?