Which Brave Roy
I've got one that's +Atk -Def and +Spd -Res.
Which one should I keep and should I then merge them or save one as a Galeforce folder?
+spd/-res is his best IV overall. Roy's optimal setup is attack > get countered > follow-up attack, which charges Galeforce (especially with horse buffs), with Fury dropping him into D3 range. This allows him to murder the next target, run to safety, or even clear out the map if you've got WoM dancers.