I am in the formative stages of a Drow campaign, and I am stuck on a few points. My plan is to take players from level 1 to 2 pretty quickly, but from that point, levels will come at a fairly slow pace. I plan to cap out at 6 unless the campaign continues for a long period afterwards, though any further levels will come extremely slowly, and almost certainly nothing higher than 8.
Part of my problem, is that I do not plan to have the city scale to the players' level. I am going to set the levels of the vast majority of 'nameless' NPC's and only make adjustments for specific NPC's for story purposes. While there will be some overriding storyline elements, a big part of what I'd like is to have a sandbox city where the PC's can try carve out a power base, and change the political and social landscape of the city. That being the case, I want to avoid changing the power levels around them.
Question #1: What is an appropriate CR for most noble house soldiers? (Soldiers, in this case means any NPC of any class that is not in a position of power, or is not unique for story purposes.) Keep in mind that I don't want the players to be absolutely paralyzed at levels 1 and 2, but I also don't want them to absolutely dominate the field at levels 5 and 6.
Question #2: How high is too high for the most powerful NPC's in the city? Should a Matron Mother be almost unassailable, even as a solo encounter (CR 12+)? Or just extremely difficult (CR 10-ish)? Should there ever be an NPC that the players have no hope of defeating?
Question #3: Is there a good way of establishing the relative power levels of NPC's, and communicating that to the players without just outright saying, "You can handle this," or "This is beyond you."
Question #4: How would the PC's discern power levels? Would a combination of Diplomacy (gather information), Knowledge (local), Knowledge (nobility), Perception, and Sense Motive checks work? Should it be a combination of checks (and how would that work?) or "one and done - and you get a power level estimate".