I'm totally new to Baldur's Gate, and started my first play through a couple of weeks ago. I think I understand most of the games rules now, but there are still a few things I don't understand. Like why is not possible for an character to wear more than one magical equippment item? For example I can't wear a cloak of protection and an ring of protection at the same time.

It's just a rule you have to accept, nothing which makes sense. In older AD&D games you could wear several items together but only gained the protection bonus from one of them.

IIRC, the official PnP allows characters to have more than one protection item on them at a time - however the effects do not stack (this kind of behavior can be seen in Neverwinter Nights to some degree).

If you are really worried about it, the BG Tweakpack has a component that enables multiple usage of protection items.

Not really worried about it, just found it a tad bit annoying. Just gonna have to live with it

I find the Tweak Pack > P&P Restrictions to be a nice middle ground. You cannot use more than one AC bonus, but you can use other items for their Saving Throw bonus. (You have to modify the item first by equipping it, then on the main screen hit the use inventory button and use the item to remove the AC bonus, then equip it again along with your armor)

All of the items that are incompatible with each other are listed in the ITEMEXCL.2DA file, which should be in your override folder. Adding or removing items to that file will affect whether they give the error ingame. I would suggest leaving the actual "X of Protection" items on the list, though, because those really ARE supposed to be exclusive, but this way you can still wear them along with armor.

You can edit the file in Notepad. Each line is an item code, followed by a 1. Just delete the lines for items (below the "VALUE" line, don't mess with anything above that) you don't want to be exclusive. In my copy, I just left the lines for CLCK01, CLCK02, CLCK31, RING06, RING07, RING25, RING41, and AMUL14... those are all the rings, amulets, and cloaks of protection, so those work like before. You may want to make a backup of the file just in case.

Thanks for the tips, that sounds easy enough, I'll give it a try.

When playing Icewind Dale with some mates at a LAN we decided to allow multiple items like this. I'd really only recommend it for higher difficulties as having -11 AC is somewhat ridiculous.

Believe it or not, it does not make a very big difference in the long run:

Fighter gear without multiple prot items:
Full Plate + Ring of Prot +2 + Claw of Kazgaroth + Cloak of Balduran + Helm of Balduran = -4 AC

Fighter gear with multiple prot items:
Full Plate +1 + Ring of Prot +2 + Ring of Prot +1 + Cloak of Prot +2 + Helm of Balduran + Amulet or Prot +1 = -7 AC

So in BG1, the difference is only 3 AC.

3 AC for 6 party members is quite a lot.

That's why I left the various protection items in the itemexcl.2da file, because wearing a whole host of them together is just silly. In BG1+2, it will net you only 1-2 extra AC per character, unless you grab the Ring +3 from the Deck of Many Things. It also allows you to stack the protection items with things like dragon scale or ankheg plate armors, which you should be able to do because they aren't enchanted in the standard sense. In base BG2, you COULD stack the protection items with dragon scale and ankheg plate, which was changed in ToB.

The non-stacking is discussed in literature somewhere. It's due the cause of the effect. Most AC bonuses come in the form a magical force-field/time-space warp effect that either slows weapons around them just a little bit or just helps glide the weapon around the armor. The more the slowing/gliding, the better the +.

So if you have 2 or 3 objects that are +1 AC (let's say full plate +1, ring of prot +1, cloak of prot +1), their effect doesn't actually stack. They all just give the exact same field.

However, dodge bonuses in 3.0 and up (I don't remember 2.0 and down having them, but I could be wrong) make your character more apt to dodge a weapon altogether. Those effects stack. A glove that helps you defend with a dodge +1 and springy boots that help you dodge +1 with 3.0 rules would stack to the +2 -- but only if you're not flatfooted. A sneak attack will go right through your dodge.

That's the way I understand it, anyway. It might give you a better appreciation for the RP elements of the non-stacking nature of the equipment.