"white" armour is generally a term used by historians for highly polished steel plate armour.

"plate" is a term which covers all steel plate armour - which could be painted, blued or blackened to prevent corrosion, or even covered in velvet or similar fabric - "white" armour is simply a subset of the larger group of plate armour finishes.

Armour plating is heavy plate steel, or other strong metal, used to create armour on a structure or vehicle.

Full plate armour, helm and gauntlets

Yes, Range protecting armour is plate armour or chain armour. Plate works best. A good Magic protection armour is D'hide. This will block any spell, it won't make them hit 0's but it does effect their hit by a lot. it's like going to the elemental wizards and being level 3 with green d'hide and 1 defence and they can only hit 1s on you (10s or under since the new 1=10 update) Melee defence is just regular old plate.

Chainmail was eventually replaced by hard plate armour.