The AC may be a discrepancy, though between the drow enforcer and the aeon guard I believe NPCs may simply ignore maximum dexterity limits. This is not explicitly stated anywhere, but it probably should be if that is in fact the reasoning. Unfortunately, even that explanation is not entirely consistent, since there are other examples of NPCs with proper armor that still have ACs matching the monster creation tables, completely ignoring their equipment.
The Create Darkness ability is not a mistake, as NPC and PC abilities may explicitly differ despite narratively being the same race. You may also notice that both NPC drow have spell resistance, while the PC racial stats provide no such bonus. In both cases, they are abilities that NPC drow possess that PC drow will not.
Drow NPC are built with different rules than Drow PCs, yes.
Unlike in Pathfinder, in Starfinder NPCs have different stats than PCs, and are built using different rules. Player race stats are often a stripped down version of the monster's full abilities, so they can be relatively balanced in a party.
Monsters and NPCs have their AC and other statistics determined largely independent of their gear. It's explained on page 127 of the Alien Archive under "Using an Array".
or in this case one of my players taking a liking to the drow enorcer and "uhm I can't build this"Once again its the Starfinder copout that monsters just have whatever stats you want with some vague guidelines because that's easier. Making NPCs and monsters follow PC rules is too hard, so just do whatever you want.
Which incidentally makes it more difficult for new players to make decisions. Since they only see the Core Book rules and try to make decisions based on the abilities available it's completely confusing when NPCs break those rules. It also leads to the very off result that NPCs have AC 18 and deal 1d10 damage, because their CR says so. But then a PC equips the same armor and weapons and is AC 15 and does half the damage.
It certainly can be frustrating, but there was a reason the game was designed the way it was. Making mind-control less likely to result in a TPK, reducing the need for a dedicated healer, allowing more "monstrous" races to be balanced when in a party, streamlining monster creation, and allowing for backward monster compatibility, just to name a few. I don't necessarily agree with all of these things, though they do seem to work as intended.
Of course, as the GM, you have the ability to change any of this. Nothing's stopping you from just letting your PC Drow have spell resistance and create darkness, or giving all your PCs a flat level to damage from first level.
The NPC arrays are the greatest thing Paizo has ever done in my opinion. I am the type of person who spends too much time making NPCs that die or don’t really matter. So having basic stats for a character of a certain CR makes games go faster. If you don’t like it then don’t use it. But to complain about a feature that you don’t have to use is pretty narrow minded in my opinion.
“It’s not fair the NPCs are made differently than PCs.” 1) Stop meta thinking. In a fight you shouldn’t know someone’s stats. 2) If you don’t like it don’t use it.