Low elo fizz won't use E+flash ever because hes too stupid to do that.
Low elo fizz won't cancel R animation inside his Q ever because he just can't do it.
Low elo fizz sucks at farming.
Low elo fizz maxes wrong abilites in most matchups (example- high elo fizz would max W against yasuo, leblanc, lissandra, low elo fizz would always max E)
Low elo fizz builds lich bane as a first item, high elo fizz builds morellos/abyssal or before CDR changes gunblade. I still love gunblade tho, it's simply perfect on top lane against tank ekko, you can outdamage him and ousustain him with that.
I'm playing fizz for years, i tried milions of builds but i'm usualy following fatefalls builds. My favorite build for fizz was in S4 after Lich bane got nerfed so i was just building cdr boots with DFG... that was OP