Elemental Damage

Research

Does this change?

If I use a skill on a plant foe thats Level 20 and A ranger that does 50 fire damage would it change if I used it on a Shiroken ranger or something different.

Also would it change if I used a different 50 damage attack that did Cold or Earth...

Yeah, holy damage does double whatever only elemental damage... nothing else
Destroyers are immune or whatever to fire damage... not talking about that just simple creatures

Hopefully this makes some sense...
If not I can try to clarify...

Since Shiro'ken are higher than lvl 20, your fire attack will deal less damage. As for specific resistances, I don't think Shiro'ken are naturally weak or strong to any particular type of element--though logically, being constructs, they should be weak against lightning. Unfortunately, elemental resistance/weakness doesn't play a huge role in PvE.

Judging from that itself, it would make sense that if you took a level 20 plant and a level 20 Shiro'ken, you would do more damage to the plant with fire damage than to the Shiro'ken. But you also have to take into consideration that natural resistances/weaknesses aren't the only difference between them. As Sante_Kelm said, Shiro'ken are typically above level 20, which means they'll have higher armor, which makes them more resistant. But if everything else is constant between the two, a plant will take more fire damage.

For your other questions:

Yes, the plant would not take extra damage since the elemental damage is not fire, and the wiki doesn't say if Shiro'ken are weak against any other element. So theoretically, both the plant and the Shiro'ken should take 50 damage.

Holy damage just doubles against undead foes. For everything else it typically ignores armor.

They are resistant to fire, and immune to the burning condition. Yet have -20 armor against cold damage.

In addition to Sante_Kelm: All (or most) monsters have an armor-rating of LVL*3 + a class bonus (+10 for sin, derv, ranger [ranger monster get the +30 against elemental dmng], +20 for para and war)

60 is the base armor, that means hitting a lvl 20 caster (monster or player) with elemental dmg will deal excactly deal the dmg mentioned in the skill description. Hitting a higher lvl monster (or a class with armor bonus) will result in lower dmg.

And yes, elemental resistances are not that much important in the game. And destroyers are immune to burning - not fire dmg. (So you should not run a Searing Flames build against them). But bringing ice instead of fire for DAMAGE reasons against destroyers is a bad idea, because fire and ice deal equal little dmg to them (ice spells deal lower dmg compared to fire spells)

What I was wondering if one type of creature would take more damage than another if the only difference was the type of creature or type of damage done to that creature

It depends on the type of creature. Some creature types are naturally weak or resistant to certain elemental types, such as plants are weak to fire. If you click on the specific elemental types in that wiki article, it'll list all of the monsters weak or resistant to that type.

yes, depending on the creature and damage type.

OP: It's all in the details. Elemental damage is typically NOT armor-ignoring. As such, the ele damage you do will be dependant on the armor your foe has versus that element. Holy damage IS armor-ignoring. However, it only does double damage versus undead. You mentioned destroyers. Please note that there is a difference between FIRE and BURNING. They are immune to burning, not to fire. They have RESISTENCE to fire, which is similar to having better armor versus fire. You may also note that some air magic spells have additional armor penetration, which means a high-armored foe will typically take more of the damage from one of these spells than they would from another source.

This doesn't prevent you from bringing Spirit of Winter and having all your nasty fire spells doing cold damage to them. Searing Flame still won't work though (due to no burning).

Probably not the most efficient build, but if you have a friend with three heroes, you could lay a lot of cold AoE hate.