I hate knowing Kaguya's Last Spells in concept but never being able to execute them more than anything. They'd make up for my really really sloppy plays for the most part.
By the way, outside of a few spots (Wriggle, Marisa and certain Keine, Kaguya and Eirin cards), is it better just to plow through as Youmu or grazefarm? on easymodo.
I'm pretty sure the extra points you get just from the 6B point items should more than offset the difference of even a clear on 6A. I no-focused pretty much every spell/nonspell simply because it's easier than paying attention to the meter on bosses and the payoff difference isn't that significant unless you're against a serious score-runner. I focus Stardust Reverie and sometimes Reisen's first/last cards to make sure I can cap them, and her last nonspell if I remember to switch my meter over to phantom. Not sure if Eirin's nonspell is worth it, but it very well might be, I should probably be doing that... The only cards I think would be worth worth grazing for Nether are Keine midboss and her last two boss cards, Wriggle's last card, and maybe some Mystia stuff (not sure if people do it on easy). None of Marisa's stuff is really worth grazing as far as I can tell, though Reimu has a few good cards. Aside from Hourai Jewel and Kaguya's first, second, and fourth timeouts, you can pretty much ignore any stage 6 spells since the spellcard bonus from finishing it quickly with Youmu is probably more significant than any small amount of extra time you'd get from going for almost-timeouts on those cards with Yuyu. Optimally you would no focus constant fire the third and fifth timeouts, but I usually mostly focus through those just to make sure I cap them.
Also, another tip (probably obvious) is to preserve familiars if possible. Always focus-kill stage fairies with familiars and switch back to Youmu to push yourself back to the human side before you collect the point items. For bosses, only shoot them if they're practically impossible to kill (eg. Milky Way, Buddha's Stone Bowl) or if they respawn (Wriggle familiars, Marisa midboss familiars, etc), in which case you can just kill them as much as you like until the boss starts buzzing and then finish off the phase once more come out (Marisa spawns them slowly, so you may want to wait for the last 2-3 seconds to finish just to be sure).
Aside from my basic "get a pretty decent score" tips, you might want to check out some easy mode replays on Royalflare for more graze spots and just use whichever ones you think you can pull off consistently enough.
