1. Original Sin is pretty good about this, most quests have more than one solution and take into account things you can do.
2. Your stats do not alter your dialogue options.
3. There is not much pre-placed loot. There's some stuff you can see, paintings and goblets and plates are worth stealing and selling. Anything in a container is random. Sometimes it's a few magic items, but other times it's uninteresting. There's no breaking into a safe to get specific items.
