For each one...
Hardest
EoSD: Royal Flare
PCB: Xanadu of Straight and Curve, same for Extra version
IN: Imperishable Shooting
MoF: Red Frog of Houei Era 4
SA: Philosophy of a Hated Mind
UFO: Tie between Rainbow UFOs, Undefined Darkness, Nightmare in Heiankyou, Grudge Bow of Genzanmi Yorimasa
TD: Stupid Miko's False Exorcism, Wild Deserted Island, Mamizou Danmaku in Ten Transformations
Most fun
EoSD: And Then Will There Be None?
PCB: A lot of the nonspells that aren't all streaming, Mesh of Light and Darkness, Danmaku Bounded Field
IN: WOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
MoF: Froggy Braves the Elements, Mishaguji-Sama
SA: Youkai Polygraph, Rorschach in Danmaku
UFO: Danmaku Chimaera, Nightmare in Heiankyou, Grudge Bow of Genzanmi Yorimasa
TD: Wild Deserted Island, Mamizou Danmaku in Ten Transformations