If you have the Mod, BG2 Tweaks, you can get unlimited stacking of gems, arrows, bullets, scrolls etc. That mod can not only be installed in BG2, but also in Tutu and BGT. Tutu and BGT allow you to play BG1 with the BG2 game engine which is why you can install BG2 Tweaks there.
The mods, of which there are hundreds, allow you to have extra NPCs, more quests, better visual effects and the like.
Here is what BG2 lets you do:
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #1036 // Make Cloakwood Areas Available Before Completing the Bandit Camp -> All of Cloakwood Except the Mines: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #1080 // Add Bags of Holding: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #1090 // Exotic Item Pack: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #1100 // Reveal City Maps When Entering Area: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #1110 // Add Map Notes: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #1120 // Stores Sell Higher Stacks of Items: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #2040 // Universal Clubs: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #2060 // Weapon Styles for All: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #2140 // Expanded Dual-Class Options: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #2151 // Wear Multiple Protection Items -> No Restrictions: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #2170 // Cast Spells from Scrolls (and Other Items) at Character Level: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #2200 // Multi-Class Grandmastery (Weimer): v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #2210 // True Grandmastery (Baldurdash): v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #3000 // Higher HP on Level Up -> Maximum: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #3010 // Maximum HP for NPCs (the bigg) -> For All Creatures in Game: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #3031 // Easy Spell Learning -> 100% Learn Spells and No Maximum Cap: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #3040 // Make Bags of Holding Bottomless: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #3080 // Unlimited Ammo Stacking: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #3090 // Unlimited Gem and Jewelry Stacking: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #3100 // Unlimited Potion Stacking: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #3110 // Unlimited Scroll Stacking: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #3121 // Happy Patch (Party NPCs do not complain about reputation) -> NPCs Can Be Angry About Reputation but Never Leave (Salk): v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #3125 // Neutral Characters Make Happy Comments at Mid-Range Reputation: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #3190 // Rest Anywhere (Japheth): v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #3200 // Sellable Items (Icelus): v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #4000 // Adjust Evil joinable NPC reaction rolls: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #4031 // Consistent Stats: Edwin -> Use BG2 Values: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #4041 // Consistent Stats: Jaheira -> Use BG2 Values: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #4061 // Consistent Stats: Minsc -> Use BG2 Values: v14
~BG2_TWEAKS/SETUP-BG2_TWEAKS.TP2~ #0 #4071 // Consistent Stats: Viconia -> Use BG2 Values: v14
You yourself choose which of these options to install.
There is a thread on this site devoted to mods which is most helpful.
I would always have BG1 NPC Project installed as it improves BG1 no end.
Some mods are a little buggy, but most are fine. They don't usually cause game crashes.
There are some mods that conflict with each other but they are well documented. In those cases you have to choose between two mods.
I have so far not bought EE because there are so many variations of mods that I have not tried yet.
However, I might just splash out as soon as I know that EE is bug-free.