I have obtained these items on NG (not NG+). I'm also still on zero flags, since the two "bosses" I've completed aren't flagged like the others. I'm still hunting for other unique enemies like this.
This game is very reasonable to SL1 at any difficulty because of cheese; the game was clearly designed with an understanding of BSII's combat and its highlights/pitfalls but it inadvertently steps into at least two really big ones. Maybe a few bosses will have clever ways to bypass the cheese but I haven't run into any yet.
I haven't solved achieving the alternate endings/true ending in a single cycle, and I don't think it's possible because the other big bosses are behind flags that do trigger. This should reduce the minimum number to two cycles from the guide's proposed three cycles though.