so im semi new to game, but lets say i have 4 weapons all with their own unique variant, do they all stack with my other variants on my armor and the other weapons as long as i have them equipped? or do they only play in effect for the weapon their linked to?
Unique Variants
A weapon's unique variant only affects that weapon. For example, if I have a Flourish with Attack Speed Increase Medium and a Brandish with Charge Time Reduction Medium, the Brandish does not benefit from the Flourish's Attack Speed Increase, and the Flourish does not benefit from the Brandish's Charge Time Reduction.
Now for armor, the armor Unique Variants will stack with whatever other Unique Variant(s) you have on your other armor piece. For example, if I have a Cobalt Helm with Stun Resist Medium, and Cobalt Armor with Stun Resist Low, then (while wearing both of them) I have the equivalent of Stun Resist High. These two UVs can total together to be greater than Maxiumum too. For example, if the same Cobalt Helm had Stun Resist High instead and the Cobalt Armor had Stun Resist Maximum, I would have an combined resistance to stun that is better than a Maximum UV.
Does that answer your question?
Depends on the items.
For weapons it only has any effect on the weapon while actively being used. For your torso and helmet it depends on the UV: status resistances are accumulative (three bars of fire defense plus two bars of fire defense equals five bars of fire defense, 3+2=5), damage defense bonuses are averaged between the two (helmet with ten bars of normal with a torso with zero bars of normal ends up with five bars of normal, 10+0/2=5). For your shield it only affects the shield (defense against damage types or status; does not affect armor, only helps while your shield is actively in use).