I don't know where you're going with any of that.
Flandre is more memorization than anything, since half of her cards are completely static :V
Hibachi isn't just memorization, it's a lot of sightreading and reflex. Same goes for Larsa.
Also, no, you can't plow through Larsa's battle using bombs, since, much like a Touhou Extra stage boss, she is immune to them.
I don't see what you're trying to say with "With flandre, it is an extra stage, so you don't even have any powerups." You um, do have powerups-- not to mention, to even get to Hibachi or Larsa, you have to play through 2 intense loops of DoDonPachi or through the lunacy that is Mushi Futari ULTRA/God mode. Flandre's 5-minute stage is a joke in comparison.