I understand the confusion, really, I do!
Please do not confuse a Tweakpack with a Fixpack.
Tweakpacks allow you to bend the rules. Fixpacks help the rules be applied more consistently. Hope that makes sense. What makes it even more confusing is that BG2 Fix looks a lot like BG2 Tweak.
Fixpacks fix stuff that's broken, like alignment corrections, kit IDs that don't show up where they're supposed to, stuff that Baldurdash fixed, and a little more. There are some people that argue that they fix too much, but I don't want Mornmaster Arval glowing red when I cast detect evil, thanks. Anyway, that isn't the point. EasyTutu already incorporates all the game-breaking stuff, so don't apply the BG2 Fixpack available at G3, or any other fixpack, to your Tutu installation!
Tweakpacks let you do more, like have unlimited arrow stacks, or lose ghastly helmet animations. It also adds containers to Tutu, and a whole lot more. You can use any tweak pack you like. I, personally, use 5, at different points in my installation.
Right after I install EasyTutu, I install Tutufix v 17. EasyTutu includes all of the core fixes, so they are skipped. I install some of the tweakish components.
After that I install BG1 NPC Kitpack. That lets me pick kits for the NPC cast of BG1. A tweak, really.
Toward the end, I install Ashes of Embers, a tweaks mod that allows me to allow warlike cleric to use martial weapons, and otherwise bases the ability to use weapons on stats rather than traditional rules. After that, I install BG2 Tweakpack from G3, and install things like exotic items, revealed city maps, and containers. In many ways, the Tweakpack replaces the Ease of Use mod. After that, I install the convenience tweaks from Sword Coast Strategems, also a G3 mod. I particularly like the ability to skip CK and to separate NPC pairs.
So, 5 tweak mods, all for the same installation. That's a lot of tweaks.