in addition I would like to ask if somebody could list of some good hidden powers and spreads that don't need 31 for Gen 7 legendaries that are used as special attackers (excluding HP Ice for Xurkitree, Nihilego and Koko).
Tapu Koko: HP Fire (used in VGC vs. Kartana, also good for Ferrothorn and Magnezone in OU)
Tapu Lele: HP Fire (standard HP used because Steel types)
Tapu Fini: HP Fire (for Ferrothorn, Kartana and Scizor)
Nihilego: HP Fire (again, for Ferrothorn and Scizor mostly)
Xurkitree: HP Water (for the Z-Rain Dance set), HP Ground (for Marowak and Magnezone)
As for spreads, all HP Fire: 31/[Even]/31/30/31/30
HP Ground: 31/x/31/30/30/31
HP Water: 31/[Even]/30/30/31/31