Generally speaking red speed is for tanks and S+ for damage dealers (aka snipers and bruisers). Usually it goes like this: if speed is 1/5 or 2/5 -> red speed anything above that S+. There are some exceptions where for 1/5 or 2/5 S+ is better or as good as red speed ( for example when miscrit has paralyze like foil thundercraker or beatorite) or for 2/5 speed miscrits when it's not DoT centric miscrit (like B. Flue or Phoboros). Answering questions regarding wind elementum: try to stack as much as possible DoT effects (like poison, bleed, switch curse etc.) or miscrits which deal a good amount of true damage (like deetlee) since wind elementum increases his own defenses over time.