You can verify these things by looking at which nebula the skill trees are in. Red = Warrior; Blue = Mage; Green = Thief. (I actually didn't notice that for a while)
Well, some warriors go for light armor because it's quicker, different perks, etc., but I think it's mostly used by stealth based characters.
It's only quicker if you don't have the "Conditioning" perk in Heavy Armor. My Nord Warrior just recently got the "Conditioning" perk, and it's a night and day difference between his speed and sprint duration with full Heavy Armor on.
I am doing 2h weapons (greatsword) and light armor - playing mostly as warrior. I did it mostly for weight reasons bit also to play for max level eventually i will thief and mage too