IEEP is a thing, what I really suggest to leave alone, unless you know how to use it well
You can use it to extract stuff from the game, which uses Infinity Engine, and modify those and thus create own customized items and all that, but frankly, if you have never done anything such, then better not. VERY easy to mess all up. As for items, then many things for BG1 and BG2 work the same way: simply copy the files to 'override' folder and play the games. If it's some new, specific item, you can get it in-game by using CLUAConsole:CreateItem("xxxx") or something like that. Have to have the debug mode turned on though.
Oh, and it's also sort of "cheating"
Not as big as with, say, ShadowKeeper, but still.