Questions about armor bonuses and stacking.

So, my wife and I started playing recently, and we are level 10 (W/N amd Mo/Me)... but we are a little confused with the armor system. I've already searched alot on guildwiki, on this site, a few other sites, and google to no avail. I have a feeling lots of people think this is obvious, but I'm uncertain as to how this plays out. So, on to my question:

How do the bonuses on armor pieces stack?

For example... there is warrior armor (lets say legs) that say "+10 vs. physical" and it says non-stackable. Does this mean:
A1) That buying two pieces of that armor (say legs and chest) are worthless because the legs give the +10 to physical EVERYWHERE... or
B1) The legs ONLY give +10 AL vs. physical attacks that hit the legs... but other bonuses versus physical don't stack. So, if a warrior had those +10 phys legs and a +8 phys shield... they only get the +10?

And then... the monk armor says +10 vs. elemental damage, but there is no "not-stackable" note by it. Does this mean:
A2) That if you wear the whole set you actually get +40 vs elemental for everywhere on your body? OR
B2) That you get +10 on each body part, but other effects from shields, spells, whatever will stack with it?

If anyone could clear this up my wife and I would greatly appreciate it. At the moment we aren't sure if we should be bying full sets of armor we like, or mixing and matching because of our questions above.

Thanks in advance!

You only need one peice of a "Non-stackable" resist to cover your whole armor set. so what I used to do when buying tyrian armor was to mix and match a set to get all of the individual resisits (ele, cold, etc.)

It made for some unusual combinations but got the job done

The same thing goes for runes, using two minor runes of swordsmanship doesn't give you +2 swords for example, one one kind of rune counts they dont stack.

Thank you for the quick response! That is what we thought (and were hoping) for the warrior armor!

So, do you (or anyone else) know about the monk armor that does NOT say it is not-stackable (i.e., I assume it is stackable). Does that also affect the entire body... so buying it all IS worthwhile because it will grant you a +40 vs elemental damage if you have all 4 pieces?

Thanks again! The help is very much appreciated!