the NPCs would just appear in the middle of nowhere on a planet with nothing of note nearby, not even a settlement (though it was in a system of an opposing power, if memory serves)
This is a slightly tricky one - that looks utterly disproportionate in non-Powerplay (or Powerplay v1) terms because surely there's nothing a player can be doing there other than hiding and recharging their shield. But in Powerplay v2, "scan NPCs" is a scoring action and they don't have to be Power NPCs for it to count.
Non-Power NPCs will appear in that sort of location - they have done for years - and a Power-aligned player can sit "nowhere on a planet" and scan those NPCs for merits and system progress (and maybe shoot them too, in some cases, though that might attract other sorts of attention). So having the possibility of Power NPCs showing up too means that they can't do that unopposed.
So some of this is just NPCs showing up where they shouldn't, or too aggressively - they can't be so tough that they defend the systems themselves, they certainly shouldn't show up outside a Power controlled/contested systems, there's a good case for the jurisdictions around Engineer bases to be neutral zones, etc. But ... there's also a definite change in the Powerplay 2 design such that "being in a foreign Power's system" is almost intrinsically a hostile act, so should attract a lot more attention than it previously has - in the same way that the Thargoids treat being present in certain of their systems as intrinsically hostile. That's not going to be to everyone's tastes, but it's something I'm certainly looking forward to personally as an opt-in change from the "I shoot you in the face, which doesn't stop us being Allies" consequence-free/light gameplay elsewhere in ED.