Question

i discovered that thundurus,tornadus and landorus have new forms but are there any other additions like new moves or better stats or something?

Answer 1

It is said that Thundurus will have more focus in Special attack, while Tornadus will have more focus on Speed, Def, and Special defense.
Landorus is supposed to be focused in attack.
Pokemaster's news

So far there is no more information.

Comments

Will these affect their natures? Or its like IVs?

---

No, it would have no effect on natures or IVs, but their base stats will be different which means Thundurus for example will end up with higher Sp.Atk.