Do effects that instruct me to cast a copy of a spell (e.g. Spelltwine, Isochron Scepter, Elite Arcanist) trigger "whenever you cast a spell" abilities, as found in Prowess, Charmbreaker Devils, etc?
I'm conscious that copying a spell on the stack (a la Pyromancer's Goggles) doesn't count as casting that spell, but I'd like to be clear on whether casting a copy counts.