I'm currently playing Pools of Darkness and thoroughly loving it. I just wrapped up killing Thorne and returned back to the Realms. As you know you have store your equipment with Elminster before you go to the outer realms. Anyways once I got all my original equipment returned to each party member I found that my armor class values for some of my characters wasn't as low as it was prior to going to Thorne's stronghold. So my question is how does the Gold Box games handle Cloaks of Displacement, Rings of Protection, Rings of Invisibility, Rings of Blinking bonuses? etc...

The AC bonus from Rings and Cloaks of Protections does not stack with the AC bonus from magical armour, but they do stack with the AC bonus from Bracers. The AC bonus from Cloaks of Displacement stacks with both Bracers and magical armour.
In addition the first physical attack against a character wearing a CoD should be an automatic miss.
Also unknown if wearing items of Protection confer bonus to Saving Throws if worn with magical armour.

Rings of Invisibility only works partially. You can still move away from melee without provoking an Opportunity Attack, but they don't make the wearer untargetable (although it may be that unequipping and equippin them at the end or start of a round will help).

Rings of Blinking works by making the wearer untargetable after he has completed his round. So they are extra effective for characters with 18-19 Dex (that means in practice 99% of all player generated characters, I bet).

Thanks for the clarification Petrus. What armor, ring, bracer, etc... configuration is ideal for best AC? It seems like wearing no armor at all ends up granting the lowest AC. Not sure. So the ring of blinking makes the wearer untargetable after they attack? That's pretty powerful if I'm understanding it correctly.

The optimal combo is Bracers AC 2 (better than regular Plate) and Rings and Cloaks of Protection. Helms and Belts also stack in some of the GB games.
This gives max movement as well as max Saving Throw bonuses, and also better AC than magic armour + CoD. Yes, it's very powerful. Especially when enemies still try to melee the character to no avail.

Where did each cloak come from?

IIRC, Cloaks of Displacement and Boots of Speed found in Pools are not quite identical to ones that were brought over from Secret. This will explain a number of AC differences.