for the Garuda>Ifrit fight I rather use Ifrit for Trash Mobs (stun and I feel is more dmg wise skill+autoattack) and Garuda for Bosses (Contagion <3 ) . I don t have dummy tests but I ve seen them from other uses and based on my exp I rather stick to it.

I m not in turn 4+ yet so can t tell as much about Acc miss atm my smn has:
Body/Head AF+1
Full DL
Relic+1

I always use Buttons but so far I didn t see Garuda or I missing it might change in turn 4+ altho keep in mind if you are only doing Turn 4-5 the whole week (and you wont) and do nothing else acc isn t as usefull compared to the rest of the game s content