I'm currently working on my first 4t3 conversion, and when I put it in game I noticed there's some distortion happening on the pointer fingers (nowhere else). I thought maybe I accidentally did it in Blender, but I checked and everything looks normal. Does anyone know what could be happening?

Looks like stray bone weights. You can try using MTK to transfer bone weights from a known good reference mesh, or in Blender, cut off and replace the hands.

Interesting... I just looked at the reference mesh I used (afBodyAirForceRecruit) and it has the same problem. I wouldn't have expected that from an EA mesh! I just found another reference mesh and that fixed the problem, but can you still explain cutting off and replacing the hands in Blender? I don't think I know what that means exactly and it might come in handy (no pun intended) at some point. What would be the steps for that?

Something I like to do is to use the original nude geoms (by cloning afNudeTop + afNudeBottom, or the relevant ones for the age/gender you're working with, and exporting the highest LOD) for adding the body pieces to the clothing because they already have their bone assignments vs using .obj body templates.
Then you can use the 'Replace only empty bone assignments' option in MTK when you're copying bones from a reference, so that it only gives assignments to the clothing and doesn't touch the body.

The limitation is that if you're following an existing tutorial they often predate the GEOM tools and expect you to be working with formats that don't retain bones, so you'd have to shoehorn in where to do this independent of instructions given. The 4t3 tutorial linked in a previous thread for example, still uses Milkshape- a program that I wouldn't let touch my CAS projects even with a very long stick

Yeah... I was able to get away with not using Milkshape this time (I think, I'm not quite in the clear yet), but I couldn't figure out how to make it work without using TSRW and OBJs/WSOs. I'd love to do it purely with GEOMs but I think I'm still too much of a beginner to know what exactly needs to be done for everything to work properly—mainly how to create a base package, because I tried the method of making a clone with S3OC and then replacing everything in S3PE, but then that leaves those extra XML files referencing the original textures that I didn't know what to do with. When I tried deleting them I was unable to use CASt in game. There's also the fact that auto-creating morphs in MTK is SO much more straightforward with WSOs, but maybe there's an easier way to do that with GEOMs that I'm not aware of.

I do know of this tutorial on avoiding Milkshape and I'm guessing you could modify it to work with GEOMs, but I don't think it was made with beginners in mind as it doesn't go into a whole lot of detail for each step. Like... I don't even know what seams are, let alone why I need to fix them lol. Same with aligning normals. I will probably make another thread at some point to ask for more clarification on everything because I'd really like to understand all technical aspects! For now I'm stuck blindly following tutorials and just hoping I'm doing the right things.