Tapu Koko - This thing will completely dominate smogon OU, considering it will most likely be fast, has good resists and decent defences, and ontop of that, an ability that gives its stab 1.5x, pretty much adaptability but with the added benefits of electric terrain for both tapu koko and its teamates. Guessing this will be the strongest of the Tapu's as it most likely has the most speed.

Tapu bulu - This thing is the only Tapu im not really sure about. It could go either way depending on its stabs.

Tapu fini - definately OU material, great typing, offensively and defensively, can switch into a plethora of ou pokemon, immune to keldeo's burns etc.

tapu lele - this thing is gonna be amazing in vgc, literally so good, but in smogon format I am unsure. Even so, this thing is gonna completely change the vgc meta, wow. stopping priority is insane in a vgc format.

What other pokemon are gonna change shit up lmao