With the new rules for NPC stats in Starfinder, there's no longer a direct connection between NPC KAC/EAC and their other stats. Normally, this isn't too much of an issue, but it adds a weird problem when considering what happens when an NPC gains the encumbered condition.
While encumbered, you reduce each of your movement speeds by 10 feet, reduce your maximum Dexterity bonus to AC to +2, and take a –5 penalty to Strength- and Dexterity-based checks.
How exactly does reducing an NPC's max DEX bonus to AC to +2 affect their KAC/EAC under this system, or does it even have any effect at all?
Keep in mind that there are creatures that have in their stat line:
+3 dex mod
Armor with +0 EAC, +1 KAC, +6 max dex bonus
EAC 10 / KAC 12
Say you have an NPC with a +3 dex mod and wearing armor with a max dex bonus of +6. The armor's max dex bonus is reduced to +4, but the dex bonus is only +3, so no effect.
Now, say you have an NPC with a +3 dex mod and wearing armor with a max dex bonus of only +3. The armor's max dex bonus is reduced to +1, so it would be prudent to apply a -2 penalty to both KAC and EAC (the absolute AC may not be tied to dexterity, but other conditions that penalize dex also penalize AC accordingly).
That being said, I personally wouldn't run my game that way. I don't have armor dex bonuses at the ready at the table; instead I would automatically apply a -2 AC penalty to any NPC with the encumbered condition for expediency's sake.