question 1: NO BEST BUILD 
, only different advantages.and disadvantages
there are possibilities
your build
100 weapon/light/ice (prot/garment)
100 weapon/fire 80 light 20 ice (ARMOR)
100 weapon/fire x light y cold (x+y=100)(prot/armor)
or
100 weapon/fire/ice question 2: nuke: pur int damage, flying spear: mag. and phys damage(with imbue)
nuke would hit pure str hardest, flying spear would hit pure int hardest
nuke deals a bit higher damage but flying dragon can crit