Alright, I finally decided to try oblivion one last time >.>
So this is basically what I decided.
I decided that oblivion stealth is pretty much inferior to action-adventure stealth in every way.
Including assassination, stealth, and those free-running parts as well.
However, the only thing that action-adventure stealth games could NEVER have is the stealing part in oblivion. Therefore, I decided to make a character based solely on stealing and only killing when necessary.

I'm already pretty sure of using wood elf, thief sign, speed and agility for attributes.

As for the class, I was going to go with the default class, Thief obviously >.>
But then I was confused when I looked at the other stealth classes as well.

I mean, how exactly are an agent, acrobat, and a thief different?

As for the skeleton key thing, first, I don't like going through dungeons at all, and also, it ruins part of the thief aspect of the game imo, when all you do is just keep clicking one single button to open the door.

thanks

The default classes are different in their Major Skills/Favored Attributes combo.