Literally every question you have is answered in the video. He is 4th level Wood Elf thief and he took moderately armored feat instead of ability increase at 4th level because that way he could increase his dexterity to 18 and get to wear medium armor to get AC to 17. You get penalty to stealth from wearing medium armor but he said that he doesn't care because he doesn't use stealth.
Anyways, how can you even play the game if you didn't get those answers from watching the video? I mean those answers literally hits in your face and you didn't get them, lord have mercy.
Penalty to stealth is mitigated by wood elf anyways and the guy abuses invis pots as well, so who needs stealth when you have true invis to guarantee surprise attacks and first turn from backstab. Potion of Speed on top to get an extra turn over the enemy as they derp around plotting next turn. Brilliant combat design.
