Replaying the game over and over and over again (people want someone to upload those spell card graphics to the wiki), so far up to hard modo, some changes:
*Ichiyou, Nezu, and Fuma get new portraits and sprite animations, that are used when declaring their spell card. (We've already seen Fuma's on the extra stage, well, those are also on the main game).
*Fuma's 4th card on hard modo 異神「パズズ&ドラゴンズ」/ Other Gods "Pazuzu & Dragons" (and presumably lunatic modo, 大悪魔「顕現する七つの大罪」 / Great Demons "Seven Deadly Sins Manifesting", i still haven't done that) replaces its triangular formation of white bullets with a circle of pink heart bullets.
*Fuma's last spell 「フーマ・ミシャンドラ」/ "Fuma Mishandra", so far on all difficulties, instead of making an spiral of stars whose "arms" go outwards in a curvy manner, the spiral "arms" go upwards and then fall again forming linear formation. Those randomized white bullets aimed at the player seem to have a higher density. Overall, the spell is all-around denser and harder.
I still lack lunatic difficulty and Nazu's cards when playing as Marisa and Sanae. Please add more info if you find something.