I, being the indecisive tool that I am, have restarted a grant total of three times, never even getting to Whiterun. This time, I'm thinking a Dunmer Ranger, specializing in Light Armor and duel-wielding. First of all, will my defense be too low to handle foes? And will my lack of focus on stealth negatively impact me joining the Thieves Guild? Should I join the Dark Brotherhood with this character instead?

Ive played through most of the thieves guild so far as a khajit with the same type of specializations as you are thinking of using and archery comes in handy a lot while sneaking especially when you get the 3x dmg sneak attack perk from using a bow. Ive gotten my archery up so high now that i can kill most targets with one arrow if not two or three at the most